Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33407 Publications

Magnetic structure in a U(Ru0.92Rh0.08)2Si2 single crystal studied by neutron diffraction in static magnetic fields up to 24 T

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

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Permalink: https://www.hzdr.de/publications/Publ-26166
Publ.-Id: 26166


Magnetic field induced tunneling and relaxation between orthogonal configurations in solids and molecular systems

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

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Permalink: https://www.hzdr.de/publications/Publ-26165
Publ.-Id: 26165


Neutron imaging of froth structure and particle motion

Heitkam, S.; Rudolph, M.; Lappan, T.; Sarma, M.; Eckert, S.; Trtik, P.; Lehmann, E.; Vontobel, P.; Eckert, K.ORC
This article 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, enabling a spatial resolution of less than 200 micron to be achieved at a frame rate of more than 1 Hz. A forced drainage setup allows the liquid content of the foam to be controlled. The averaged attenuation of the neutrons is demonstrated to yield the liquid fraction of the foam. Hydrophobized gadolinium particles with a diameter of 200 microns 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 at different rates. An avalanche-like motion of particle clusters is observed. Neutron radiography is demonstrated to yield unique insights into the unsteady froth flotation process.
Keywords: Neutron imaging, Flotation, Froth, Particle Tracking

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Permalink: https://www.hzdr.de/publications/Publ-26164
Publ.-Id: 26164


Coarsening evolution of dendritic sidearms: from synchrotron experiments to quantitative modeling

Neumann-Heyme, H.; Shevchenko, N.; Lei, Z.; Eckert, K.ORC; Keplinger, O.; Grenzer, J.; Beckermann, C.; Eckert, S.
The local dynamics of dendritic sidearms during coarsening are studied by combining in-situ radiography observations with numerical and analytical models. A flat sample of a Ga-In alloy is partially solidified and then held isothermally in a vertical temperature gradient. The evolving dendritic microstructure is visualized using synchrotron X-ray imaging at the BM20 (ROBL) beamline at ESRF, France. During the coarsening stage, the temporal evolution of the geometrical features of sidebranches is captured by automated image processing. This data is used to quantify the dynamics of two basic evolution mechanisms for sidebranches: retraction and pinch-off. The universal dynamics of sidearm necks during pinch-off are exploited to determine the product of liquid diffusivity and capillarity length, Dd_0, as a parameter that is crucial in the calibration of quantitative models. By employing an idealized phase-field model for the evolution of a single sidebranch, the behavior of selected sidebranches is reproduced from the experiments in a consistent way.
Keywords: Dendritic solidification; microstructure; coarsening; sidearm detachment; X-ray radiography; phase-field model; material properties

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Permalink: https://www.hzdr.de/publications/Publ-26163
Publ.-Id: 26163


Structural and thermodynamic investigation of AnIVLI(O)HOPO(Article)

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

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Permalink: https://www.hzdr.de/publications/Publ-26162
Publ.-Id: 26162


Calibration of scintillation screens for ultrashort electron bunch detection

Kurz, T.; Couperus, J. P.ORC; Krämer, J. M.; Ding, H.; Kuschel, S.; Köhler, A.; Zarini, O.; Hollatz, D.; Schinkel, D.; D‘Arcy, R.; Schwinkendorf, J. P.; Irman, A.; Schramm, U.; Karsch, S.
This work reports on the calibration of scintillating screens for diagnoses of high-charge density electron beams origination from laser plasma accelerators (LPA). Our setup at the conventional ELBE accelerator is cross-calibrated with an integrating current transformer (ICT) and allows for calibration over a large charge density range, thus enabling the study both the linear and non-linear scintillating screen response, as well as long-term stability tests of the screens. In contrast to previous works, the calibration presented here is performed under conditions with a close mimic to real experimental LPA conditions.
A linear response of the scintillator to the applied electron charge was found, followed by a saturation process starting in the range of nC/mm^2. Mimicking a 1-Hz LPA, long–term stability tests showed a significant decrease of the scintillation efficiency over time.
Finally, we present a method where a LED-based constant light source provides an easy method for absolute calibration of charge diagnostic systems at LPAs. This method eliminates many potential error sources existing in currently used methods and enables the transfer of absolute charge calibrations between laboratories.
  • Poster
    3rd European Advanced Accelerator Concepts Workshop, 24.-30.09.2017, Isola d'Elba, Italy
  • Invited lecture (Conferences)
    Joint ARIES-ADA Workshop on 'Scintillation Screens and Optical Technology for transverse Profile Measurements', 01.-03.04.2019, Kraków, Polska

Permalink: https://www.hzdr.de/publications/Publ-26161
Publ.-Id: 26161


Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator

Couperus, J. P.ORC; Pausch, R.; Köhler, A.; Zarini, O.; Krämer, J. M.; Kurz, T.; Garten, M.; Huebl, A.; Gebhardt, R.; Helbig, U.; Bock, S.; Zeil, K.; Debus, A.; Bussmann, M.; Schramm, U.; Irman, A.
Laser-plasma wakefield acceleration is capable of producing quasi-monoenergetic electron beams reaching into the GeV range with few-femtoseconds bunch duration. Scaling the charge to the nanocoulomb range would yield hundreds of kiloamperes peak-current and stimulate the next generation of radiation sources covering high-field THz, high-brightness X-ray and γ-ray sources, compact FELs and laboratory-size beam-driven plasma accelerators. Laser-plasma accelerators generating such high currents operate in the beam loading regime where the accelerating field is strongly modified by the self-fields of the injected bunch, improving the final beam quality if appropriately controlled. Here we experimentally investigate the effects of beam loading at the theoretically predicted limit by loading unprecedented charges of about 0.5 nC within a mono-energetic peak into the first plasma cavity. As the energy balance is reached, the final energy spread is minimized. We show that the beam quality is maintained up to an estimated peak-current of 50 kA, an order of magnitude larger than in state-of-the-art conventional and laser-plasma accelerators.
  • Lecture (Conference)
    3rd European Advanced Accelerator Concepts Workshop, 24.-30.09.2017, Isola d'Elba, Italy
  • Lecture (Conference)
    Conference on High Intensity Laser and attosecond science in Israel (CHILI), 11.-13.12.2017, Tel-Aviv, Israel

Permalink: https://www.hzdr.de/publications/Publ-26160
Publ.-Id: 26160


Research on the chemistry of f-elements at HZDR - A general overview of the division Chemistry of the f-Elements

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

Permalink: https://www.hzdr.de/publications/Publ-26159
Publ.-Id: 26159


Drone-borne hyperspectral monitoring of acid mine drainage. An example from the Sokolov lignite district.

Jackisch, R.; Lorenz, S.; Zimmermann, R.; Möckel, R.; Gloaguen, R.
This contributions aims to demonstrate the potential of unmanned aerial systems (UAS) to monitor areas affected by Acid mine drainage (AMD). The investigated area covers a recultivated tailing, which is and part of the Sokolov coalmine district in the Czech Republic. A high abundance of AMD minerals occurs in a confined space of the selected test site, which AMD minerals in high abundances can signal potential environmental predicament. The deposited mine waste material contains pyrite and itsthe consecutive weathering products, mainly iron hydroxides and oxides, which affect the natural pH values of the Earth’s surface. While previous research done in this area relies on satellite and air-borne data, our approach focuses on lightweight drone systems providing ground readiness within hours and, thus,, enabling rapid field campaigns. High spatial image resolutions and and precise target determination are additional advantages of UAS-based mapping. During April to September 2016, in total four field and flight campaigns were conducted. For validation, the waste heap was probed in-situ for pH, X-ray fluorescence (XRF) and, reflectance spectrometry. and sSampling points were surveyed by a differential GNSS global navigation satellite systems. Ground truth was achieved by collecting samples that were characterized for pH, X-ray diffraction and XRF in laboratory conditions. Sampling points were surveyed by a differential GNSS global navigation satellite systems. Hyperspectral data were processed and corrected for atmospheric, topographic and illumination effects. High-resolution point clouds and digital elevation models were built from drone-borne RGB data using Structure-from-Motion. The supervised classification of hyperspectral image (HSI) data suggests the presence of jarosite and goethite -, minerals associated with the acidic environmental conditions (pH range = 2.3 – 2.8 in situ). We identified specific iron absorption bands in the UAS-HS data, and was confirmed with ground-truth spectroscopy. The distribution of in-situ pH data supports the UAS-based mineral classification results. Evaluation of the applied methods highlights the drone surveying as a fast, non-invasive, inexpensive technique for multi-temporal environmental monitoring of the post-mining landscape.
Keywords: Hyperspectral; Remote sensing; unmanned aerial system; Acid mine drainage; Iron minerals; Image classification, Sokolov, post-mining

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Permalink: https://www.hzdr.de/publications/Publ-26158
Publ.-Id: 26158


Ion Beam Induced Surface Modification of ta-C Thin Films

Berova, M.; Sandulov, M.; Tsvetkova, T.; Kitova, S.; Bischoff, L.; Boettger, R.
Thin film samples (d ~ 40 nm) of tetrahedral amorphous carbon (ta-C), deposited by filtered cathodic vacuum arc, were implanted with Ga+ at ion energy E = 20 keV and ion fluences D = 3E14 - 3E15 cm-2 and N+ with the same energy and ion fluence D = 3 E14 cm-2. The Ga+ ion beam induced surface structural modification of the implanted material, displayed by formation of new phase at non-equilibrium condition, which could be accompanied by considerable changes in the optical properties of the ta-C films. The N+ implantation also results in modification of the surface structure. The induced structural modification of the implanted material results in a considerable change of its topography and optical properties. Nanoscale topography and structural properties characterisation of the Ga+ and N+ implanted films were performed using atomic spectroscopy analysis. The observed considerable surface structural properties modification in the case of the higher fluence Ga+ implanted samples results from the relatively high concentration of introduced Ga+ atoms, which is of the order of those for the host element.
Keywords: carbon, ion implantation, atomic force microscopy

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Permalink: https://www.hzdr.de/publications/Publ-26157
Publ.-Id: 26157


Visualization of gas-liquid multiphase pseudo-slug flow using Wire-Mesh Sensor

Kesana, N. R.; Parsi, M.; Vieira, R. E.; Azzopardi, B.; Schleicher, E.; Mclaury, B. S.; Shirazi, S. A.; Hampel, U.
Intermittent two-phase flows are commonly encountered in the petroleum industry. Much attention has been focused by several researchers on intermittent flows existing at low superficial gas velocities (<10 m/s). There is limited work performed on intermittent structures persisting at higher superficial gas velocities (pseudo-slug flows). In the present experimental study, a conductivity-based Wire-Mesh Sensor (WMS) was used to visualize and characterize pseudo-slug flow. Experiments were performed in a 76.2 mm horizontal pipe with air and water as the working fluids at atmospheric conditions. The superficial gas and liquid velocities ranged from 9 m/s to 35 m/s and 0.45 m/s to 0.76 m/s, respectively. A 16 × 16 WMS was placed 17 m away from the pipe inlet to measure spatio-temporal void-fraction distribution. The WMS data acquisition frequency was set to 10 kHz. From the void-fraction time series data, the periodic pseudo-slug structures were visualized. The visualization suggested that unlike slug flow where the liquid structures fill the pipe cross-section, the pseudo-slugs were extremely aerated structures (high gas-liquid mixing) formed due to the gas penetration into the liquid slug body. This paper also presents the measurements of important hydrodynamic characteristics such as cross-sectional averaged void-fraction time series and mean void fraction. The effect of liquid viscosity on the visualized structures is also presented.
Keywords: Flow visualization Intermittent multiphase flows Pseudo-slug flow Slug flow Wire-mesh sensor

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Permalink: https://www.hzdr.de/publications/Publ-26156
Publ.-Id: 26156


Fission and other fast neutron induced reactions investigated at nELBE

Beyer, R.ORC; Junghans, A. R.; Dietz, M.; Kögler, T.; Schwengner, R.; Urlaß, S.; Wagner, A.
The nELBE neutron time-of-flight facility provides neutrons in the energy range from about 10 keV up to 10 MeV with an intensity of about 10⁴ n/s/cm². The combination of the superconducting electron accelerator ELBE and a compact liquid lead neutron production target delivers neutron bunches within a time spread of a few picoseconds and a repetition rate of 100 to 400 kHz (cw) enabling high resolution time-of-flight measurement even with flight paths of only 5 to 11 meters. At nELBE different types of fast neutron induced nuclear reactions can be and have been investigated, ranging from total neutron cross section measurement over elastic and inelastic scattering to neutron induced fission. E.g. the neutron induced fission cross section of Pu-242 has been measured in the range from 0.5 to 10 MeV relative to U-235(n,fis) using two fission ionization chambers. A statistical uncertainty down to 1.1 % and systematic uncertainty of about 2.7 % was reached.
Keywords: nELBE, neutron time-of-flight, transmission, inelastic scattering, fission
  • Poster
    LANL FIESTA Fission School & Workshop, 17.-22.09.2017, Santa Fe, New Mexico, USA

Permalink: https://www.hzdr.de/publications/Publ-26155
Publ.-Id: 26155


Fission measurements at nELBE

Beyer, R.ORC; Dietz, M.; Junghans, A. R.; Kögler, T.; Schwengner, R.; Urlaß, S.
The nELBE neutron time-of-flight facility provides neutrons in the energy range from about 10 keV up to 10 MeV with an intensity of about 104 n/s/cm2. The combination of the superconducting electron accelerator ELBE and a compact liquid lead neutron productiontarget delivers neutron bunches within a time spread of a few picoseconds and a repetition rate of 100 to 400 kHz (cw) enabling high resolution time-of-flight measurement even with flight paths of only 5 to 11 meters. At nELBE different types of fast neutron induced nuclear reactions can be and have been investigated, ranging from total neutron cross section measurement over elastic and inelastic scattering to neutron induced fission. E.g. the neutron induced fission cross section of 242Pu has been measured in the range from 0.5 to 10 MeV relative to 235U(n,f) using two fission ionization chambers. A statistical uncertainty down to 1.1% and systematic uncertainty of about 2.7% was reached.
Keywords: nELBE, neutron time-of-flight, fission
  • Invited lecture (Conferences)
    LANL FIESTA Fission School & Workshop, 17.-22.09.2017, Santa Fe, New Mexico, USA

Permalink: https://www.hzdr.de/publications/Publ-26154
Publ.-Id: 26154


Magnetic field induced strong valley polarization in the three-dimensional topological semimetal LaBi

Kumar, N.; Shekhar, C.; Klotz, J.; Wosnitza, J.; Felser, C.
LaBi is a three-dimensional rocksalt-type material with a surprisingly quasi-two-dimensional electronic structure. It exhibits excellent electronic properties such as the existence of nontrivial Dirac cones, extremely large magnetoresistance, and high charge-carrier mobility. The cigar-shaped electron valleys make the charge transport highly anisotropic when the magnetic field is varied from one crystallographic axis to another. We show that the electrons can be polarized effectively in these electron valleys under a rotating magnetic field. We achieved a polarization of 60% at 2 K despite the coexistence of three-dimensional hole pockets. The valley polarization in LaBi is compared to the sister compound LaSb where it is found to be smaller. The performance of LaBi is comparable to the highly efficient bismuth.

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Permalink: https://www.hzdr.de/publications/Publ-26153
Publ.-Id: 26153


Charge Density Waves in Graphite: Towards the Magnetic Ultraquantum Limit

Arnold, F.; Isidori, A.; Kampert, E.; Yager, B.; Eschrig, M.; Saunders, J.
Graphite is a model system for the study of three-dimensional electrons and holes in the magnetic quantum limit, in which the charges are confined to the lowest Landau levels.We report magneto-transport measurements in pulsed magnetic fields up to 60 T, which resolve the collapse of two charge density wave states in two, electron and hole, Landau levels at 52.3 and 54.2 T, respectively. We report evidence for a commensurate charge density wave at 47.1 T in the electron Landau level, and discuss the likely nature of the density wave instabilities over the full field range. The theoretical modeling of our results predicts that the ultraquantum limit is entered above 73.5 T. This state is an insulator, and we discuss its correspondence to the “metallic” state reported earlier.We propose that this (interaction-induced) insulating phase supports surface states that carry no charge or spin within the planes, but does, however, support charge transport out of plane.

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Permalink: https://www.hzdr.de/publications/Publ-26152
Publ.-Id: 26152


Magnetic field induced phase transitions and phase diagrams of multiferroic Mn0.95Co0.05WO4 with cycloidal spin structure

Urcelay-Olabarria, I.; Ressouche, E.; Wang, Z.; Skourski, Y.; Ivanov, V. Y.; Popov, Y. F.; Vorobev, G. P.; Balbashov, A. M.; Qureshi, N.; Garcia-Munoz, J. L.; Skumryev, V.; Mukhin, A. A.
Slightly Co-doped MnWO4 at the lowest 5% Co concentration, for which the multiferroic cycloidal phase becomes a ground state, has been studied in magnetic fields up to 60 T by bulk magnetic and electric polarization measurements along different crystallographic directions. The field induced magnetic transitions up to 12 T and the ways they proceed were tracked also by single-crystal neutron diffraction, and the relevant field induced magnetic structures were identified and refined. The complete magnetoelectric phase diagrams for magnetic fields along distinct directions in relation to the cycloidal spin structure have been constructed for magnetic field values exceeding those necessary to induce a spin-flip transition into the paramagnetic state. Their common feature is the existence of nonpolar sinusoidal phases identified by the disappearance of the electric polarization in a field regime slightly below the spin-flip transition. At lower magnetic fields either continuous or abrupt field induced reorientations of the cycloidal magnetic structures were observed, respectively, for a field direction along the crystallographic b axis or along the easy magnetic axis, and the different character of those transitions has been attributed to specific features in the magnetic anisotropy.

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Permalink: https://www.hzdr.de/publications/Publ-26151
Publ.-Id: 26151


Influence of MOCVD Growth Pressure on Magnetoresistance of Nanostructured La-Ca-Mn-O Films Used for Magnetic Field Sensors

Zurauskiene, N.; Pavilonis, D.; Klimantavicius, J.; Balevicius, S.; Stankevic, V.; Kersulis, S.; Plausinaitiene, V.; Abrutis, A.; Lukose, R.; Skapas, M.; Juskenas, R.; Knasiene, B.; Naujalis, E.; Law, J. M.
The results of structure and magnetoresistance (MR) of nanostructured La1−xCaxMnyO3 (LCMO) films, grown at different gas pressure (from 3 to 7 Torr) by pulse injection metal–organic chemical vapor deposition (MOCVD) technique, are presented. The MR was investigated in pulsed magnetic fields up to 60 T in the temperature range 1.5–294 K. The results were analyzed from the perspective of using these films for magnetic field sensors operating at low temperatures. It was demonstrated that with the increase of Ar + O2 gas pressure, the surface morphology of the films becomes rougher and grain size increases. Also, the ratio of Mn/(La + Ca) increases with the increase of the pressure. Large MR of the films was observed in a wide temperature range below the ferromagnetic–paramagnetic phase transition. It was shown that at cryogenic temperatures, the films grown at gas pressure of 3 Torr have higher sensitivity in lower magnetic field range (<10 T), while in high magnetic fields (20–60 T), the properties of films grown at higher gas pressure 5–7 Torr are favored. The obtained results allow evaluating the influence of MOCVD growth pressure on MR and sensitivity to the magnetic field of LCMO manganites used for pulsed magnetic field sensors.

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Permalink: https://www.hzdr.de/publications/Publ-26150
Publ.-Id: 26150


Structural and Magnetic Properties of the Trirutile-type 1D-Heisenberg Anti-Ferromagnet CuTa2O6

Golubev, A.; Dinnebier, R. E.; Schulz, A.; Kremer, R. K.; Langbein, H.; Senyshyn, A.; Law, J. M.; Hansen, T. C.; Koo, H.-J.; Whangbo, M.-H.
We prepared trirutile-type polycrystalline samples of CuTa2O6 by low-temperature decomposition of a Cu−Ta−oxalate precursor. Diffraction studies at room temperature identified a slight monoclinic distortion of the hitherto surmised tetragonal trirutile crystal structure. Detailed high-temperature X-ray and neutron powder diffraction investigations as well as Raman scattering spectroscopy revealed a structural phase transition at 503(3) K from the monoclinic structure to the tetragonal trirutile structure. GGA+U density functional calculations of the spin-exchange parameters as well as magnetic susceptibility and isothermal magnetization measurements reveal that CuTa2O6 is a new 1D Heisenberg magnet with predominant anti-ferromagnetic nearest-neighbor intrachain spin-exchange interaction of ∼50 K. Interchain exchange is a factor of ∼5 smaller. Heat capacity and low-temperature high-intensity neutron powder diffraction studies could not detect long-range order down to 0.45 K.

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Permalink: https://www.hzdr.de/publications/Publ-26149
Publ.-Id: 26149


Coordination polymer (CP) networks and molecular complexes of tetravalent actinides (Th, U, Np) with aromatic polycarboxylate ligands or polyoxometalate (POM) species

Loiseau, T.ORC; Martin, N. P.; Volkringer, C.; Duval, S.; März, J.; Ikeda-Ohno, A.ORC
Coordination polymers are built up from the association of metallic centers with organic (e.g. O- or N-donor) ligands. In the particular case of actinides (An), precedent studies have reported mainly the synthesis of such solid networks bearing U(VI) or Th(IV), while trans-uranium elements have been much less studied due to their high radiotoxicity and limited amount of the material source. Among the possible oxidation states of An, the tetravalent state has been investigated most actively and large polyoxo clusters have been isolated for U or Pu. In contrast, there are very few data concerning Np(IV) compounds. The knowledge of the formation of such polynuclear An(IV) species could be of significant importance for the fate of An in contaminated soils containing O-donor ligands, such as humic acids, or other organic pollutants (e.g. phthalates).
In the present communication, we firstly present the formation of several series of uranyl-organic frameworks associated to poly-carboxylate linkers, by following the pH variation parameter of the reaction medium, related to the hydrolysis rate. This strategy was then applied to actinides(IV), which are known to exhibit a strong affinity for hydrolysis reaction in order to form inorganic entities with high nuclearities. In a first approach, the control of water content in reaction media containing organic solvent will be investigated in different chemical systems with Th(IV) and U(IV) in the presence of dicarboxylic acids molecules (typically terephthalic acid), and was then extended to Np(IV) for some cases. The structural descriptions of the different coordination polymers will point out the nuclearity variation of the inorganic bricks from mononuclear [AnO9] up to hexanuclear entities [An6O8]. The particular case of the poly-oxo cluster [An38] will be discussed, and its formation will be described with U(IV) and Np(IV) in different solvents. The crystallization of the crystallization of U(IV) and Np(IV) with various aromatic polycarboxylate ligands was then considered in water medium and crystal structures of coordination networks with phtalate and mellitate have been analyzed. The last point deals with the isolation and crystallization of polynuclear clusters of actinides (Th(IV)/U(IV)) embedded within large anionic polytungstate moieties ([SiW9O34], [AsW9O33]). Trinuclear, tetranuclear and hexanuclear motifs bearing actinides(IV) have thus been identified in this system.
Keywords: Actinides, tetravalent, coordination polymers, carboxylates, polyoxo-metalate, metal-organic frameworks
  • Invited lecture (Conferences)
    American Chemical Society Annual Meeting, 22.-28.03.2018, New Orleans, USA

Permalink: https://www.hzdr.de/publications/Publ-26148
Publ.-Id: 26148


QMOM methods for bubbly flows –potentials for simulation of pumps

Hasse, C.; Salenbauch, S.; Pollack, M.; Oertel, R.; Li, D.; Schlegel, F.; Lucas, D.
The temporal and spatial development of a particle size distribution, e.g. in a bubbly flow, can be described with the so-called Population Balance Equation. It represents a continuity statement for the number density of particles in a flow. The presentation contains a comparison of two prominent approaches for solving the population balance equation, i.e. the family of Quadrature-based Moment Methods and the Method of Classes.
Keywords: Population Balance Modeling, Quadrature-based Method of Moments, Class Methods, Pumps
  • Lecture (others)
    VDMA AK-Mehrphasenströmung, 26.09.2017, Frankfurt, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-26147
Publ.-Id: 26147


Negative Longitudinal Magnetoresistance from the Anomalous N = 0 Landau Level in Topological Materials

Assaf, B. A.; Phuphachong, T.; Kampert, E.; Volobuev, P. S.; Mandal, P. S.; Sanchez-Barriga, J.; Rader, O.; Bauer, G.; Springholz, G.; de Vaulchier, L. A.; Guldner, Y.
Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current. We perform pulsed and dc field measurements on Pb1−xSnxSe epilayers where the topological state can be chemically tuned. The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial. In a topological material, the lowest N = 0 conduction Landau level disperses down in energy as a function of increasing magnetic field, while the N = 0 valence Landau level disperses upwards. This anomalous behavior is shown to be responsible for the observed NLMR. Our work provides an explanation of the outstanding question of NLMR in topological insulators and establishes this effect as a possible hallmark of bulk conduction in topological matter.

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Permalink: https://www.hzdr.de/publications/Publ-26146
Publ.-Id: 26146


Interplay between localization and magnetism in (Ga,Mn)As and (In,Mn)As

Yuan, Y.; Xu, C.; Hübner, R.; Jakiela, R.; Böttger, R.; Helm, M.; Sawicki, M.; Dietl, T.; Zhou, S.
Ion implantation of Mn combined with pulsed laser melting is employed to obtain two representative compounds of dilute ferromagnetic semiconductors (DFSs): Ga1−xMnxAs and In1−xMnxAs. In contrast to films deposited by the widely used molecular beam epitaxy, neither Mn interstitials nor As antisites are present in samples prepared by the method employed here. Under these conditions the influence of localization on the hole-mediated ferromagnetism is examined in two DFSs with a differing strength of p-d coupling. On the insulating side of the transition, ferromagnetic signatures persist to higher temperatures in In1−xMnxAs compared to Ga1−xMnxAs with the same Mn concentration x. This substantiates theoretical suggestions that stronger p-d coupling results in an enhanced contribution to localization, which reduces hole-mediated ferromagnetism. Furthermore, the findings support strongly the heterogeneous model of electronic states at the localization boundary and point to the crucial role of weakly localized holes in mediating efficient spin-spin interactions even on the insulator side of the metal-insulator transition.

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Publ.-Id: 26145


ASTEC model development for the severe accident progression in a generic AP1000-LIKE

Albright, L.; Wilhelm, P.; Jevremovic, T.
Improvements in light water reactor (LWR) technologies in recent decades have led to the development of advanced LWRs, currently under construction, soon to join the international fleet of nuclear power plants (NPPs). Enhanced safety capabilities have been achieved in advanced LWRs through the utilization of passive safety systems and design improvements. The progression of severe accidents in advanced LWRs is not well described in the current open literature. To date severe accident analyses performed on the Westinghouse AP1000 have focused on evaluating the performance of the AP1000 safety systems in the prevention of severe accidents, with little focus on characterizing the progression of core degradation to identify the timing of key events such as core uncovery, relocation of corium to the lower plenum, and lower head failure.

An initial, generic model of an AP1000-LIKE reactor has been developed in the severe accident integral code ASTEC to characterize the progression of severe accidents in the AP1000-LIKE model and identify the representation of important physical phenomena and key events of core degradation progression. To evaluate the progression of severe accidents in the AP1000 an accident scenario without accident management measures (AMM), and a complete loss of primary flow is designed and simulated using the developed ASTEC model. The preliminary code results showed the applicability of the model to simulate severe accident scenarios. Without AMM, it is determined that reactor pressure vessel failure occurs nearly four hours after the start of the transient; after the loss of primary coolant flow, a large amount of hydrogen is produced (~800 kg), and a large mass of molten material forms (~150 tons) and relocates to the lower plenum. Future efforts will focus on developing a full plant model for a generic AP1000 and further characterizing the progression of severe accidents.
Keywords: Severe Accidents, Westinghouse AP1000, ASTEC
  • Contribution to proceedings
    IAEA Technical Meeting on the Status and Evaluation of Severe Accident Simulation Codes for Water Cooled Reactors, 09.-12.10.2017, Vienna, Austria
    Status and Evaluation of Severe Accident Simulation Codes for Water Cooled Reactors, Wien: IAEA, 9789201029195
  • Lecture (Conference)
    IAEA Technical Meeting on the Status and Evaluation of Severe Accident Simulation Codes for Water Cooled Reactors (I3-TM-54660), 09.-12.10.2017, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-26144
Publ.-Id: 26144


Molecular and Crystal Structures of Uranyl Nitrate Coordination Polymers with Double-headed 2-Pyrrolidone Derivatives

Kazama, H.; Tsushima, S.; Ikeda, Y.; Takao, K.
Double-headed 2-pyrrolidone derivatives (DHNRP) were designed and synthesized as bridging ligands for efficient and selective separation of UO22+ from HNO3 solution by precipitation. The building blocks, UO2(NO3)2 and DHNRP, were successfully connected to form an infinite 1D coordination polymer. Solubility of [UO2(NO3)2(DHNRP)]n is no longer correlated to hydrophobicity of the ligand, but is exclusively governed by ligand symmetry and packing efficiency. The newly designed DHNRP family can be used to establish a new spent nuclear fuel reprocessing scheme.

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Publ.-Id: 26143


Interaction of NpO2+ with Cl– in NaCaCl-type solutions at ionic strength of 6M: Effect of presence of Ca ion on interaction

Nagasakia, S.; Saito, T.; Tsushima, S.; Goguen, J.; Yang, T.
The interaction of NpO2+ with Cl– was studied using visible–near-infrared spectroscopy in NaClCaCl2NaClO4, NaClNaClO4, and CaCl2NaClO4 solutions with ionic strength (I) of 6M. The spectra of NpO2+ around 980 nm varied with Cl– concentration in the NaClCaCl2NaClO4 and NaClNaClO4 solutions at [Cl–] ≥ 3.5M, but not in the CaCl2NaClO4 solution. Assuming the 1:1 interaction between NpO2+ and Cl–, the apparent equilibrium constants at I = 6M were evaluated. The presence of Ca2+ was found to destabilize overall interaction between NpO2+ and Cl–. The observations were consistent with the density functional theory calculation.
Keywords: Cl–, Density Functional Theory Calculation, Equilibrium Constants, Ionic Strength, NpO2+, Presence of Ca2+
  • Open Access Logo Contribution to proceedings
    37th Annual Conference of the Canadian Nuclear Society and 41st Annual CNS/CNA Student Conference, 04.-07.06.2017, Niagara Falls, Canada
    DOI: 10.1016/j.net.2017.08.010

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Permalink: https://www.hzdr.de/publications/Publ-26142
Publ.-Id: 26142


Geostatistical simulation of compositional data in the presence of several geological domains

Talebi, H.; Tolosana-Delgado, R.; Lo, J.; Mueller, U.
This paper proposes a methodology for geostatistical simulation of compositional data in presence of several geological domains: After applying statistical analysis and compositionally compliant contact analysis on the data set, geological domains with the same compositional characteristics are merged. Plurigaussian simulation (PGS) is utilized to generate multiple numerical models of the remaining domains, with the aim of assessing the uncertainty in the domain boundaries and improving the geological controls in the characterization of compositional attributes. The resulting conditional realisations of geological domains are used to derive the posterior probabilities of occurrence of the domains over the deposit. The compositional data set is classified by geological domain and for each class realisations are generated across the target grid of the resource. The final mineral resource model is obtained by weighting the simulated mineral compositions associated with the different domains by the probabilities of occurrence of each domain. This approach accounts for the uncertainty in the geology of the ore body and spatial variability of mineral composition.

The approach is illustrated through an application to a nickel-cobalt laterite deposit located in Western Australia. A set of 8818 samples is considered in order to provide the conditioning data. Four rock types (Ferruginous, Smectite, Saprolite, and Ultramafic) are considered to define compositionally homogeneous domains. Three major (Fe, Al, and Mg) and two target (Ni and Co) elements are the variables of interest in this study. Since the data are compositional a filler variable is introduced to achieve closure and to retain the intuitive relation between each component and the mass of its associated element.
  • Lecture (Conference)
    Annual Conference of the International Association for Mathematical Geosciences, 04.-07.09.2017, Fremantle, Perth, Australia

Permalink: https://www.hzdr.de/publications/Publ-26141
Publ.-Id: 26141


Geochemical Interactions of Plutonium with Opalinus Clay Studied by Spatially Resolved Synchrotron Radiation Techniques

Kaplan, U.; Amayri, S.; Drebert, J.; Rossberg, A.; Grolimund, D.; Reich, T.
Plutonium plays an important role within nuclear waste materials because of its long half-life and high radiotoxicity. The aim of this study was to investigate with high spatial resolution the reactivity of the more oxidized forms of Pu(V,VI) within Opalinus Clay (OPA) rock, a heterogeneous, natural argillaceous rock considered as a potential repository host. A combination of synchrotron based X-ray microprobe and bulk techniques was used to study the spatial distribution and molecular speciation of Pu within OPA after diffusion and sorption processes. Microscopic chemical images revealed a pronounced impact of geochemical heterogeneities concerning the reactivity of the natural barrier material. Spatially resolved X-ray absorption spectroscopy documented a reduction of the highly soluble Pu(V,VI) to the less mobile Pu(IV) within the argillaceous rock material, while bulk investigations showed second-shell scattering contributions, indicating an inner-sphere sorption of Pu on OPA components. Microdiffraction imaging identified the clay mineral kaolinite to play a key role in the immobilization of the reduced Pu. The findings provide strong evidence that reduction and immobilization do not occur as linked processes on a single reactive phase but as decoupled, subsequent, and spatially separated reactions involving different phases of the OPA.
Keywords: Plutonium opalinus clay sorption XAS ROBL

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Publ.-Id: 26140


Zur Mineralogie von Vulkaniten im Bereich des Kemmlitzer Porphyrs (Oschatz Formation, Nordwestsächsisches Becken)

Götze, J.; Lessig, F.; Möckel, R.; Georgi, U.
Kurzfassung
Mineralogische und geochemische Untersuchungen an Proben des Kemmlitzer Porphyrs sowie von Lithophysen (Hochtemperatur- Kristallisationsdomänen) im entsprechenden Verbreitungsgebiet wurden durchgeführt, um eine mineralogisch-petrographische Charakteristik dieser vulkanischen Bildungen und deren Zuordnung zu möglichen Muttergesteinen zu ermöglichen. Phasenanalytische Untersuchungen (Röntgendiffraktometrie, Mikroskopie, Kathodolumineszenz - KL) erbrachten eine monotone Mineralzusammensetzung, die von Quarz und den beiden Kalifeldspatphasen Sanidin und Orthoklas dominiert ist. Anhand der geochemischen Charakteristika (RFA) lassen sich die untersuchten Vulkanite als Rhyolithe einstufen. Das Vorkommen von hypidiomorphen Quarzphänokristen, z.T. mit Resorptionserscheinungen, gut erhaltenen Kalifeldspäten sowie das Fehlen von Glas-Shards und Fiamme (Bimsfetzen) deuten darauf hin, dass es sich bei den vulkanischen Ablagerungen im Untersuchungsgebiet um Laven und keine Pyroklastite (Ignimbrite) handelt.
Aus den deutlichen Übereinstimmungen hinsichtlich mineralogischer Zusammensetzung, chemischer Charakteristik und textureller Ausbildung kann geschlussfolgert werden, dass alle untersuchten Proben einem vulkanischen Ereignis (Kemmlitzer Porphyr) zuzuordnen sind. Auftretende Unterschiede sind im Wesentlichen auf sekundäre Alterationen zurückzuführen. Das übereinstimmende Erscheinungsbild der Phänokristen sowie deren KL-Eigenschaften deuten auf eine Herkunft aus einer gemeinsamen Schmelze hin. Obwohl die mineralogischen, geochemischen und texturellen Ähnlichkeiten von Lithophysen und Kemmlitzer Porphyr auffällig sind, konnten bisher im massiven, porphyrisch ausgebildeten Vulkanit keine sphärolithischen Bildungen nachgewiesen werden. Randliche Anhaftungen von Pechsteinrelikten an den Lithophysen verschiedener Vorkommen lassen dagegen vielmehr auf eine Bildung im Bereich einer glasigen Fazies schließen.

Abstract
Mineralogical and geochemical investigations of the Kemmlitz porphyry and lithophysae (high-temperature crystallization domains) in the associated area were carried out to get information concerning mineralogical-petrographical characteristics of these volcanic formations and their relation to possible parent rocks. An integrated analytical study by X-ray diffraction, microscopy and cathodoluminescence (CL) revealed a monotonic mineral composition dominated by quartz, sanidine and orthoclase. The rocks can be classified as rhyolite based on the chemical composition (XRF). The predominance of hypidiomorphic quartz phenocrysts, partially with resorption features, well preserved K-feldspar as well as the lack of glass shards and fiamme indicate that the volcanic rocks derive from lava flows and are not related to ignimbrites.
The investigated samples can probably be related to the same volcanic event (Kemmlitz porphyry) because of the similarities in mineral composition, chemical characteristics and texture. Detected variations mainly result from secondary alteration processes. The consistent appearance of phenocrysts and their CL characteristics indicate the origin from a common melt source. Despite these mineralogical, chemical and textural similarities between the Kemmlitz porphyry and the lithophysae, no spherulithic aggregates have been found within the massive porphyric volcanics. Marginal relics of pitchstone on some of the lithophysae instead indicate their formation in a glassy facies.
Keywords: Porphyr, Mineralogie, Nordwestsachsen
  • Contribution to external collection
    in: Veröffentlichungen des Museums für Naturkunde Chemnitz, Chemnitz: Museum für Naturkunde, 2017, 133-150

Permalink: https://www.hzdr.de/publications/Publ-26139
Publ.-Id: 26139


Measurements of neutron scattering angular distributions with a new scintillator setup

Pirovano, E.; Beyer, R.; Junghans, A. R.; Nolte, R.; Nyman, M.; Plompen, A.
A new experimental setup for the measurement of neutron scattering cross sections and angular distributions is currently being developed at the neutron time-of-flight facility GELINA, at the JRC-Geel. Up to 32 liquid organic scintillators are employed for the detection of neutrons scattered from a sample of the investigated material. The differential cross section is measured at eight different angles, and the angleintegrated cross section is obtained from the differential data by numerical integration. Two experiments for the study of scattering on iron were carried out, one at GELINA and the other at nELBE (HZDR). The first results for the angular distributions of elastic scattering in the neutron energy range from 2 to 6MeV are here presented and compared with evaluations from the major nuclear data libraries.
Keywords: nELBE, GELINA, neutron, angular distribution
Related publications
Cross section and neutron angular distribution … (Id 28211) has used this publication of HZDR-primary research data

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Permalink: https://www.hzdr.de/publications/Publ-26138
Publ.-Id: 26138


Measuring at relevant concentrations – radiolabeling as a versatile tool in nanosafety research

Schymura, S.; Hildebrand, H.; Franke, K.
The employment of radiotracers is a versatile tool for the detection of nano-particulate materials in complex systems such as environmental samples or organisms. With the increasing usage of nanoparticles in applications outside of research laboratories, a careful risk assessment of their release into the environment becomes mandatory. However, the monitoring of nanoparticles in such complex natural systems as soil, natural waters, plants, sewage sludge, etc. is nearly impossible using conventional methods, especially at environmentally relevant concentrations. This obstacle can be overcome by radiolabeling, which may be of crucial value in enabling such research.
We have developed various methods of introducing radiotracers into some of the most common nanoparticles, such as Ag, carbon, SiO2, CeO2 and TiO2 nanoparticles. The labeling techniques are the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labeling utilizing the recoil of a nuclear reaction to implant a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles at elevated temperatures. Using these methods we have produced [105/110mAg]Ag, [124/125/131I]CNTs, [48V]TiO2, [139Ce]CeO2, [7Be]MWCNT, [7Be]SiO2, [44/45Ti]TiO2, etc.. The methods are adaptable for a wide range of other nanoparticles. The so-labelled nanoparticles can be detected at minimal concentrations well in the ng/L range even with a background of the same element and without complicated sample preparations necessary.
Using our methods one can radiolabel commercial nanoparticle samples for sensitive detection in environmentally relevant trace concentrations. The labeled particles have been successfully used in release studies, environmental mobility studies, fate studies in waste water treatment and plant uptake studies.
  • Poster
    Scientific Stakeholder Meeting on Nanomaterials in the Environment, 10.-11.10.2017, Dessau, Deutschland
  • Invited lecture (Conferences)
    Scientific Stakeholder Meeting on Nanomaterials in the Environment, 10.-11.10.2017, Dessau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26137
Publ.-Id: 26137


NANOSUPPE - Behavior of engineered nanoparticles in the pathway wastewater - sewage sludge - plant using the examples TiO2, CeO2, MWCNT and quantum dots

Schymura, S.; Fricke, T.; Hildebrand, H.; Neugebauer, M.; Franke, K.
The Project NanoSuppe is concerned with the behavior of nanoparticles along the pathway wastewater – sewage sludge – plant as this is one of the main expected paths in the life cycle of manufactured nanomaterials (MNMs) and marks the possible preliminary end of life of a MNM when it is removed from contaminated wastewater, as well as the potential reintroduction into the human food chain by the use of contaminated sewage sludge as fertilizer. Hence, work was conducted concerning the fate of MNMs in wastewater treatment plants by means of model WWTPs in the lab. Furthermore, environmental mobility studies concerning colloidal stability of MNMs in natural waters and their interaction with soil and sewage sludge were conducted by means of batch and column experiments. As a last step the uptake of MNMs by plants was investigated from hydroponic media as well as soil/sewage sludge matrices.
As a rather unique feature the used MNMs (TiO2, CeO2, MWCNTs and quantum dots) were radiolabeled to enable their sensitive detection at environmentally relevant concentrations in the complex matrices involved.
  • Invited lecture (Conferences)
    Scientific Steakholder Meeting, 10.-11.10.2017, Dessau, Deutschland
  • Invited lecture (Conferences)
    Scientific Steakholder Meeting, 10.-11.10.2017, Dessau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26136
Publ.-Id: 26136


Studies towards the development of a PET radiotracer for imaging of the P2Y1 receptors in the brain: synthesis, 18F-labeling and preliminary biological evaluation

Moldovan, R.-P.; Wenzel, B.; Teodoro, R.; Neumann, W.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Hey-Hawkins, E.; Krügel, U.; Brust, P.
Purine nucleotides such as ATP and ADP are important extracellular signaling molecules in almost all tissues activating various subtypes of purinoreceptors. In the brain, the P2Y1 receptor (P2Y1R) subtype mediates trophic functions like differentiation and proliferation, and modulates fast synaptic transmission, both suggested to be affected in diseases of the central nervous system. Research on P2Y1R is limited because suitable brain-penetrating P2Y1R-selective tracers are not yet available. Here, we describe the first efforts to develop an 18F-labeled PET tracer based on the structure of the highly affine and selective, non-nucleotidic P2Y1R allosteric modulator 1-(2-[2-(tert-butyl)phenoxy]pyridin-3-yl)-3-[4-(trifluoromethoxy)phenyl]urea (7). A small series of fluorinated compounds was developed by systematic modification of the p-(trifluoromethoxy)phenyl, the urea and the 2-pyridyl subunits of the lead compound 7. Additionally, the p-(trifluoromethoxy)phenyl subunit was substituted by carborane, a boron-rich cluster with potential applicability in boron neutron capture therapy (BNCT). By functional assays, the new fluorinated derivative 1-{2-[2-(tert-butyl)phenoxy]pyridin-3-yl}-3-[4-(2-fluoroethyl)phenyl]urea (18) was identified with a high P2Y1R antagonistic potency (IC50 = 10 nM). Compound [18F]18 was radiosynthesized by using tetra-n-butyl ammonium [18F]fluoride with high radiochemical purity, radiochemical yield and molar activities. Investigation of brain homogenates using hydrophilic interaction chromatography (HILIC) revealed [18F]fluoride as major radiometabolite. Although [18F]18 showed fast in vivo metabolization, the high potency and unique allosteric binding mode makes this class of compounds interesting for further optimizations and investigation of the theranostic potential as PET tracer and BNCT agent.
Keywords: Purine P2Y1 receptors Positron emission tomography Brain PET tracers Radiometabolites Micellar chromatography Hydrophilic interaction chromatography

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  • Secondary publication expected from 01.03.2020

Permalink: https://www.hzdr.de/publications/Publ-26135
Publ.-Id: 26135


P1513 - Procedure and apparatus for measuring a d.c. magnetic field based on magnetostrictive effect in magnetic wires

Bali, R.; Kolesar, V.; Vazquez, M.
The present invention relates to a procedure for measuring a d.c. magnetic field by means of a cylindrical device formed by a magnetostrictive core. A d.c. magnetic field is applied and the mechanical deformation on the device caused by the magnetic field is measured and compared with the obtained measurements from previous calibrations to estimate magnetic field intensity values. The invention also relates to an apparatus for measuring a d.c. magnetic field by means of the indicated procedure. The apparatus comprises:
- a cylindrical sensor element and an abutment/fixing element, such that the cylindrical sensor element experiences mechanical deformation when exposed to the d.c. magnetic field,
- a deformation sensing device configured for detecting the mechanical deformation of the cylindrical sensor element, and
- a processing unit configured for determining the intensity of the d.c. magnetic field based on the detected mechanical deformation of the cylindrical sensor element.
  • Patent
    EP3171189 - Offentlegung: 24.05.2017

Permalink: https://www.hzdr.de/publications/Publ-26134
Publ.-Id: 26134


Radiolabeling - an appropriate tool to study the environmental fate of engineered nanoparticles

Franke, K.; Schymura, S.; Hildebrand, H.
To study the environmental fate of nanoparticles it requires versatile tools for detection of nano-particulate materials in complex systems such as soil, sewage sludge or organisms within a wide range of concentration. Challenging are the environmentally relevant low concentrations of nanoparticles and the presence of background concentrations of the respective elements. The radiolabeling of nanoparticles offers an excellent and robust method to enable nanoparticle detection in these complex media down to the ng/L range. Even online in-situ tracing and visualization techniques are accessible to obtain spatio - temporal process information.

Depending on the nature of the nanoparticle and the process of interest different methods for the radiolabeling of nanoparticles can be applied, like the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labeling utilizing the recoil of a nuclear reaction to implant a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles.

For our recent studies we produced [44Ti]TiO2, [45Ti]TiO2, [48V]TiO2, [64Cu]CuS, [64Cu]SiO2, [65Zn]CdSe/ZnS, [105Ag]Ag, [110mAg]Ag, [124I]CNTs, [125I]CNTs, [131I]CNTs, [7Be]MWCNT, [139Ce]CeO2 and [194Au]Pt nanoparticles. Due to the choice of the used radionuclide (half-life, decay-mode) and the activity concentrations it was possible to enable different detection methods and time scales for the investigations. All these methods go along with a careful characterization of the radiolabeled nanoparticles in respect of the radiolabeling stability and nanoparticle properties.

The radiolabeled nanoparticles have been successfully used in comprehensive environmental studies, like release studies, environmental mobility studies, fate studies in waste water treatment and plant uptake studies.
  • Invited lecture (Conferences)
    NanoSafety 2017, 11.-13.10.2017, Saarbrücken, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26133
Publ.-Id: 26133


P1601 - Verfahren und Vorrichtung

Hoffmann, A.; Speck, O.
Gemäß verschiedenen Ausführungsformen kann ein Verfahren (100) Folgendes aufweisen: Erzeugen (101) eines Magnetfeldes in einem Bestrahlungsbereich; Bestrahlen (103) des Bestrahlungsbereichs mittels eines Partikelstrahls, welcher spinpolarisierte Partikel aufweist; Erfassen (105) einer Anregung der spinpolarisierten Partikel, welche durch das Magnetfeld bewirkt wird; und Ermitteln (107) einer räumlichen Charakteristik des Partikelstrahls auf Grundlage der Anregung.
  • Patent
    DE102016100638 - Offenlegung: 20.07.2017, Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-26132
Publ.-Id: 26132


P1602 - Tomographievorrichtung

Barthel, F.; Hampel, U.; Bieberle, A.
Die Erfindung betrifft eine Tomographievorrichtung mit Mitteln zum Erzeugen eines Elektronenstrahls; einer Ablenkvorrichtung zum Ablenken des Elektronenstrahls; einem Target; einer Steuervorrichtung zur Steuerung der Ablenkvorrichtung mittels Steuerungsdaten derart, dass der Elektronenstrahl an einem Auftreffpunkt auf das Target auftrifft und der Auftreffpunkt entlang mehrerer, in unterschiedlichen Ebenen verlaufender Bahnen geführt wird, wobei an dem Auftreffpunkt Röntgenstrahlung entsteht; und mehreren Röntgendetektoren zum Erfassen der Röntgenstrahlung, wobei jeder der Röntgendetektoren ein sich über alle Ebenen hinweg erstreckendes Detektorelement mit Szintillatormaterial und einen Lichtdetektor zum Erfassen von Szintillationslicht und Erzeugen eines Detektorsignals aufweist; wobei jedes der Detektorsignale basierend auf den Steuerungsdaten derjenigen Ebene zugeordnet wird, in der sich der Auftreffpunkt des Elektronenstrahls auf dem Target während der Erzeugung des Detektorsignals befindet.
  • Patent
    DE102016101787 - Offenlegung 03.08.2017, Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-26131
Publ.-Id: 26131


P1609 - THz-Antenne und Vorrichtung zum Senden und/oder Empfangen von THz-Strahlung

Singh, A.; Winnerl, S.; Schneider, H.; Helm, M.
Die Erfindung betrifft eine THz-Antenne und Vorrichtung zum Senden und/oder Empfangen von THz-Strahlung, wobei die THz-Antenne mehrere streifenförmige Elektroden und mehrere streifenförmige Gegenelektroden aufweist, die unter Ausbildung einer periodischen Elektrodenanordnung abwechselnd und parallel zueinander angeordnet sind, wobei jeweils eine Elektrode und eine Gegenelektrode ein Elektrodenpaar definieren, wobei die Elektrode und die Gegenelektrode jedes der Elektrodenpaare mittels photoleitfähigen Materials miteinander verbunden sind, und wobei die Elektroden und die Gegenelektroden mit einer konstanten Breite derart ausgebildet sind, dass die Elektroden eine größere Breite aufweisen als die Gegenelektroden.
  • Patent
    DE102016116900 - Erteilung: 02.08.2017, Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-26130
Publ.-Id: 26130


Two Point Correlation Measurements in Liquid Metal Duct Flows using Ultrasound Phased Arrays

Mäder, K.; Räbiger, D.; Nauber, R.; Büttner, L.; Eckert, S.; Czarske, J.
A key to improvements of industrial processes involving liquid metals like continuous steel casting is a good knowledge of the interaction between time-varying magnetic fields and conductive fluids. For investigations in this area, model experiments using low-melting liquid metals are conducted, which require suitable instrumentation for opaque media. Ultrasound Doppler velocimetry allows to measure the flow structures and thus to obtain turbulence statistics. For MHD experiments investigating small-scale and turbulent flows, a spatial resolution in the low millimeter range is required.
However, state of the art systems using arrays of unfocused single transducers are limited in their resolution by the divergence of the far field ultrasound beam. In addition, thus systems allow only one dimensional measurements along the propagation direction of the ultrasound beam. Thus interesting quantities in some experiments like turbulence statistics in the axial direction in duct flows can not be measured.
Using our novel phased array ultrasound Doppler velocimeter (PAUDV), the duct flow of an opaque liquid under the influence of an magnetic field can be studied. The measurement system combines the ultrasound Doppler velocimetry with the phased array technique, which allows to adaptively shape the sound field. Using its possibility to drive phased arrays with up to 256 individual channels simultaneously, the ultrasound beam is dynamically focussed in the measurement area, which increases the spatial resolution. In addition, the cross beam technique is used to enable two component measurements using a single acoustical access. This allows to measure turbulence statistics in the main flow direction of a fluid duct with only one ultrasound array on the duct wall.
Keywords: Ultrasound Phased arrays, flow measurements, liquid metals, duct flows
  • Lecture (Conference)
    16th European Turbulence Conference, 21.-24.08.2017, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-26128
Publ.-Id: 26128


Controlled ion beam hyperdoping of silicon nanowires

Berencén, Y.; Prucnal, S.; Wang, M.; Hübner, R.; Böttger, R.; Glaser, M.; Schönherr, T.; Möller, W.; Georgiev, Y. M.; Rebohle, L.; Erbe, A.; Lugstein, A.; Zhou, S.; Helm, M.; Skorupa, W.
The hyperdoping of semiconductors consists of introducing dopant concentrations far above the equilibrium solubility limits. This results in a broadening of dopant energy levels into an impurity or intermediate band. We have recently demonstrated that hyperdoping bulk Si with Se shows promise for Si-based short-wavelength infrared photodetectors [1]. Lately, silicon nanowires (NWs) have gained increasing importance as building blocks for nanodevices like field-effect transistors, light emitting devices and photovoltaic cells [2, 3]. Therefore, the comparison between hyperdoping Si nanowires and bulk Si is a common issue to be examined, which comes along with the transition from a bulk material to semiconductor NWs.
In this work, we report on non-equilibrium processing for controlled hyperdoping of Si/SiO2 core/shell nanowires previously synthesized by the vapor-liquid-solid method. Our approach is based on Se implantation of the upper half of NWs followed by millisecond flash lamp annealing, which allows for a bottom-up template-assisted recrystallization of the amorphized parts of the NWs via explosive solid-phase epitaxy. The Se-hyperdoped Si NWs are successfully recrystallized and accommodate Se concentrations as high as 1021 cm-3. As a proof of device concept, a single Se-hyperdoped NW-based IR photoconductor is shown. In this way, the combination of ion implantation and flash lamp annealing as a promising nanoscale hyperdoping technology is successfully established.
[1] Y. Berencén, S. Prucnal, Fang Liu, I. Skorupa, R. Hübner, L. Rebohle, S. Zhou, H. Schneider, M. Helm, and W. Skorupa, “Room-temperature short-wavelength infrared Si photodetector,” Sci. Rep. 7, 43688 (2017).
[2] B. Tian, T. Cohen-Karni, Q. Qing, X. Duan, P. Xie and C.M. Lieber, “Three-dimensional, flexible nanoscale field-effect transistors as localized bioprobes,” Science 329, 831 (2010).
[3] T. J. Kempa, B. Tian, D.R. Kim, J. Hu, X. Zheng and C.M. Lieber, “Single and tandem axial p-i-n nanowire photovoltaic devices,” Nano Lett. 8, 3456 (2008).
Keywords: Hyperdoping, Si nanowires, ion implantation, flash lamp annealing, impurity band, sub bandgap photoresponse
  • Lecture (Conference)
    E-MRS 2017 Fall Meeting (European-Materials Research Society), Symposium S: Materials- nanoelectronics & nanophotonics, 18.09.2017, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-26127
Publ.-Id: 26127


Development of highly potent phosphodiesterase 2A (PDE2A) inhibitors: Synthesis and in vitro evaluation of novel fluorinated tricyclic compounds

Ritawidya, R.; Scheunemann, M.; Brust, P.
Phosphodiesterases (PDEs) play an important role in degrading the cyclic nucleotide second messengers, cAMP and cGMP. They are involved in many biological processes such as neurological, immune or inflammatory disorders, cancer, and heart diseases [1]. One of the PDEs, PDE2A, is found highly expressed in distinct areas of the brain but also in certain types of cancer [1]. Our goal was to synthesize novel fluorinated tricyclic compounds (FT) derivatives which could potentially be used as radioligands for PDE2A imaging of above-mentioned diseases via Positron Emission Tomography (PET). A key intermediate (compound 5 in the respective poster) was prepared in 4 steps, starting from aniline. Afterwards, two-step Suzuki coupling reaction, as well as bromination [2,3] were employed to introduce different moieties in C-1 and C-8 position of 5 to afford three FT derivatives, so-called FT1, FT2, and FT3. They were successfully prepared in 6-8 % overall yield (7-10 steps). The inhibitory potential of these FT derivatives towards PDE2A3 and other subtypes of PDEs was estimated. The affinity and selectivity of FT1 (82.9 % inhibition of PDE2A3 at 10 nM) was much higher than that of FT2 and FT3 (8.52 % and 13.2 % inhibition, respectively). The IC50 value of FT1 was 3.33 nM. It shows selectivity against PDE1A3, 3A, 4A1, 5A1, 6AB, 7A, 8A1, 9A1, 10A1, and 11A1. It is suggested that FT1 if radiolabeled with the PET radionuclide 18F could be a promising PDE2A imaging agent. Further studies to determine the suitability of FT1 as PET candidate are still needed.
Keywords: PDE2A, Benzoimidazotriazine, PET tracer
  • Poster
    Biotechnology Symposium, 05.10.2017, Leipzig, Deutschland

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Publ.-Id: 26126


Dynamo action generated by a precession driven flow in a cylindrical container

Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.
Since many years precession is regarded as an alternative flow driving mechanism that may account, e.g., for remarkable features of the ancient lunar magnetic field or as a complementary power source for the geodynamo. Precessional forcing is also of great interest from the experimental point of view because it represents a natural forcing mechanism that allows an efficient driving of conducting fluid flows on the laboratory scale without making use of propellers or pumps. Within the project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) a dynamo experiment is under development at Helmholtz-Zentrum Dresden-Rossendorf in which a precession driven flow of liquid sodium with a magnetic Reynolds number of up to Rm=700 will be used to drive dynamo action.

Our present study addresses preparative numerical simulations and flow measurements at a small model experiment running with water. In dependence of precession ratio and Reynolds number the resulting hydrodynamic flow patterns and amplitudes provide the essential ingredients for kinematic dynamo models that are used to estimate whether the particular flow is able to drive a dynamo. In the strongly non-linear regime the flow essentially consists of standing inertial waves. Most remarkable feature is the resonant-like occurrence of a stationary axisymmetric mode which emerges around a precession ratio Ωp/Ωc = 0.1. Kinematic dynamo models applying the time-averaged flow field from the hydrodynamic simulations exhibit dynamo action at a critical magnetic Reynolds number of Rmc=430 which is well within the range that will be achieved in the planned large scale sodium experiment.
Keywords: Dynamo, DRESDYN
  • Poster
    Dynamos and planetary flows today (PHR2017), 16.-17.11.2017, London, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-26124
Publ.-Id: 26124


Engineering and modifying two-dimensional materials by electron beams

Zhao, X.; Kotakoski, J.; Meyer, J. C.; Sutter, E.; Sutter, P.; Krasheninnikov, A. V.ORC; Kaiser, U.; Zhou, W.
Electron-beam (e-beam) irradiation damage is often regarded as a severe limitation to atomic-scale study of two-dimensional (2D) materials using electron microscopy techniques. However, energy transferred from the e-beam can also provide a way to modify 2D materials via defect engineering when the interaction of the beam with the sample is precisely controlled. In this article, we discuss the atomic geometry, formation mechanism, and properties of several types of structural defects, ranging from zero-dimensional point defects to extended domains, induced by an e-beam in a few representative 2D materials, including graphene, hexagonal boron nitride, transition-metal dichalcogenides, and phosphorene. We show that atomic as well as line defects and even novel nanostructures can be created and manipulated in 2D materials by an e-beam in a controllable manner. Phase transitions can also be induced. The e-beam in a (scanning) transmission electron microscope not only resolves the intrinsic atomic structure of materials with defects, but also provides new opportunities to modify the structure with subnanometer precision.
Keywords: TEM, graphene

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Publ.-Id: 26123


Towards diluted magnetism in TaAs

Liu, Yu; Li, Z.; Guo, L.; Chen, X.; Yuan, Y.; Xu, C.; Hübner, R.; Akhmadaliev, S.; Krasheninnikov, A. V.; N'Diaye, A. T.; Arenholz, E.; Helm, M.; Zhou, S.ORC
Magnetism in Weyl semimetals is desired to investigate the interaction between the magnetic moments and Weyl fermions, e.g., to explore anomalous quantum Hall phenomena. Here we demonstrate that proton irradiation is an effective tool to induce ferromagnetism in the Weyl semimetal TaAs. The intrinsic magnetism is observed with a transition temperature above room temperature. The magnetic moments from d states are found to be localized around Ta atoms. Further, the first-principles calculations indicate that the d states localized on the nearest-neighbor Ta atoms of As vacancy sites are responsible for the observed magnetic moments and the long-ranged magnetic order. The results show the feasibility of inducing ferromagnetism in Weyl semimetals so that they may facilitate the applications of this material in spintronics.

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Publ.-Id: 26122


Substitutional carbon doping of free-standing and Ru-supported BN sheets: A first-principles study

Berseneva, N.; Komsa, H.-P.; Vierimaa, V.; Björkman, T.; Fan, Z.; Harju, A.; Todorovic, M.; Krasheninnikov, A. V.ORC; Nieminen, R. M.
The development of spatially homogeneous mixed structures with boron (B), nitrogen (N) and carbon (C) atoms arranged in a honeycomb lattice is highly desirable, as they open the possibility of creating stable two-dimensional materials with tunable band gaps. However, at least in the free-standing form, the mixed BCN system is energetically driven towards phase segregation to graphene and hexagonal BN. It is possible to overcome the segregation when BCN material is grown on a particular metal substrate, for example Ru(0 0 0 1), but the stabilization mechanism is still unknown. With the use of density-functional theory we study the energetics of BN/Ru slabs, with different types of con gurations of C substitutional defects introduced to the h-BN overlayer. The results are compared to the energetics of free- standing BCN materials. We found that the substrate facilitates the C substitution process in the h-BN overlayer. Thus, more homogeneous BCN material can be grown, overcoming the segregation into graphene and h-BN. In addition, we investigate the electronic and transport gaps in free-standing BCN structures, and assess their mechanical properties and stability. The band gap in mixed BCN free-standing material depends on the concentration of the constituent elements and ranges from zero in pristine graphene to nearly 5 eV in free-standing h-BN. This makes BCN attractive for application in modern electronics.
Keywords: graphene, doping, first-principles calculations

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Publ.-Id: 26121


Ionization and reflux dependence of magnetic instability generation and probing inside laser-irradiated solid thin foils

Huang, L. G.; Schlenvoigt, H.-P.; Takabe, H.; Cowan, T. E.
When an intense laser accelerated electron beam, with large current density on the order of 10^12 A/cm^2, enters a solid density plasma, it is well-known to be subject to a number of different types of instabilities that cause it to filament. In this work, we investigate the transport instability of a fast electron beam that is imprinted on the self-generated magnetic filaments inside the solid density plasmas using particle-in-cell simulations. By varying collisional ionization models, our simulations show that the atomic ionization process is crucial to determine the structure of the magnetic filaments. We further attribute the generation of bulk magnetic filaments to Weibel-like instability mechanism caused by counter-propagating hot forward-bulk return current streams and counterpropagating hot forward-reflux current streams. It is found that the magnetic fields in the filament channels near the rear surface are around one order of magnitude higher than those near the front surface of the thin solid target. This asymmetry is likely induced by the very different properties of bulk electron stream and hot reflux electron stream in terms of density and velocity distribution. Finally, we propose to probe the magnetic fields inside the solid density plasmas by X-Ray polarimetry via Faraday rotation using X-Ray free electron lasers (XFELs). The synthetic simulations show that XFELs are capable to detect the magnetic fields from relativistic laser-solid interactions.
Keywords: Laser plasma interactions, Weibel instability,XFEL,Faraday rotation

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Publ.-Id: 26120


Reactive transport modelling based on actual parameters obtained from GeoPET analysis of column experiments

Karimzadeh, L.; Schymura, S.; Kulenkampff, J.; Franke, K.; Eichelbaum, S.; Lippmann-Pipke, J.; Fischer, C.
Abstract

GeoPET is the application of positron emission tomography (PET) for direct, non-destructive, quantitative spatiotemporal measurement and visualization of fluid transport in natural geological media on drill-core scale [1-5]. Here, we present new results that focus on reactive transport simulations on a drill core sample in 4D (3D+t) by using velocity fields (vx, vy, vz) obtained from GeoPET measurements of a fractured rock sample.
A mechanically induced fracture was obtained during a geomechanical shear test in a calciferous sandstone drill core sampled from the Permian Kupferschiefer ore formation (Rudna mine, Poland). Column leaching experiments using the core sample (D = 6 cm, L = 10 cm) were carried out in a plexiglas reaction cell in the laboratory at atmospheric pressure. The leaching solutions were injected with constant flow rate of 1 mL/h in three stages: First, a moderately hard synthetic fresh water (pH = 8.5) was used as inflow solution for 22 days in order to remove the salts minerals. Second, an acidic solution with pH of 1.5 (H2SO4) was injected to reduce the carbonat content within another 23 days. In stage three, 0.17 mol/L concentrated ferric iron was added to the acidic inflow solution (pH 1.5, H2SO4) for 20 days in order to dissolve mainly the Cu-sulfid minerals and increase the copper recovery from sample. The tracer transport in the sample was monitored by PET technique and the velocity fields derived by using an image analysing algorithm. The velocity fields then imported in the COMSOL Multyphisics to simulate and calibrate the fluidflow. Three dimensional modeling by means of iCP 1.3[6] (an interface coupling of the finite element based code COMSOL Multiphysics® with the geochemical code PhreeqC[7]) was performed to predict the leaching process and solute transport through the core sample by using kinetic mineral dissolution and precipitation data (BRGM database). The reactive transport model results are compared and refined by using the laboratory column leaching experiments.
Keywords: Reactive transport modeling, GeoPET, Column leaching experiment
  • Poster
    Reactive Transport in the Earth and Environmental Sciences in the 21st Century, 02.-06.10.2017, Amboise, France

Permalink: https://www.hzdr.de/publications/Publ-26119
Publ.-Id: 26119


Scaling EUV and X-ray Thomson sources to optical free-electron laser operation with Traveling-Wave Thomson-Scattering

Steiniger, K.; Albach, D.; Debus, A.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.
Traveling-Wave Thomson-Scattering (TWTS) allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources by providing optical undulators with hundreds to thousands of undulator periods from high-power, pulse-front tilted lasers pulses.

With TWTS the realization of optical free-electron lasers (OFELs) as well as incoherent radiation sources with orders of magnitude higher photon yields than classic head-on Thomson sources becomes possible with state-of-the-art technology in electron accelerators and laser systems.

The talk will show how pulse-front tilted, petawatt class laser pulses and relativistic electrons work together in a side-scattering geometry, where laser end electron propagation direction of motion enclose an angle, to realize long but compact optical undulators with centimeter to meter-scale interaction distances at sub-millimeter undulator periods. Example setups of TWTS OFELs emitting ultraviolet radiation are presented which are realizable today with existing technology for electron accelerators and laser systems. Especially the ultra-low emittance of laser wakefield accelerated electron bunches can be exploited to compensate for their one percent level energy spreads. Further an experimental setup is presented to generate the tilted TWTS laser pulses. This setup strategy provides dispersion compensation, required due to angular dispersion of the laser pulse, and is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups.
Keywords: Optical free-electron laser, traveling wave, thomson scattering, vuv, euv, x-ray, laser dispersion control
  • Lecture (Conference)
    SPIE Optics + Optoelectronics, 24.-27.04.2017, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-26118
Publ.-Id: 26118


Design of optical setups for high-yield optical undulators in the Traveling-Wave Thomson-Scattering geometry

Steiniger, K.; Debus, A.; Albach, D.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.
Traveling-Wave Thomson-Scattering (TWTS) can realize ultra-compact, inherently synchronized and highly brilliant light sources from the ultraviolet to the hard X-ray range. In TWTS ultrashort laser pulses and relativistic electron bunches are utilized in a side-scattering geometry where laser pulse and electron bunch direction of motion enclose an interaction angle. Thereby the laser electric field provides the undulator field in which electrons oscillate and emit radiation during interaction. By employing tilted laser pulses TWTS ensures continuous overlap of laser and electrons while these traverse the laser cross-sectional area. Tilting the laser pulse-front compensates the spatial separation of electrons and laser at begin and end of the interaction originating from their different propagation directions. Combining laser pulse-front tilt and side-scattering in TWTS enables interaction over hundreds to thousands of optical undulator periods, enough to allow for optical free-electron laser (OFEL) operation since microbunching of the electron bunch and thus coherent radiation amplification can be achieved.
After shortly introducing the TWTS scattering geometry, the design of optical setups to generate the tilted TWTS laser pulses is presented in the talk. This setup strategy provides dispersion compensation, required due to angular dispersion of the laser pulse, and is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups. Determining parameters of the setup is illustrated in an example of an ultraviolet TWTS OFEL and an outlook is given on the design of hard X-ray TWTS sources.
Keywords: Traveling wave, thomson scattering, laser dispersion control, x-ray source
  • Lecture (Conference)
    DPG Frühjahrstagung Dresden, 19.-24.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26116
Publ.-Id: 26116


IAEA CRP benchmark of ROCOM PTS test case for the use of CFD in reactor design using ANSYS CFX

Höhne, T.
Over the last 15 years, considerable effort has been expended in assembling the available information on the use of CFD in the nuclear reactor safety field. Typical application areas here are heterogeneous mixing and heat transfer in complex geometries, buoyancy-induced natural and mixed convection, etc., with specific reference to NRS accident scenarios such as Pressurized Thermal Shock (PTS), boron dilution, hydrogen build-up in containments, thermal fatigue and thermal striping issues, etc. The development, verification and validation of CFD codes in respect to NPP design necessitates further work on the complex physical modelling processes involved, and on the development of efficient numerical schemes needed to solve the basic equations. Therefore, a set of ROCOM CFD-grade test data were made available to set up an IAEA benchmark, relating to Pressurized Thermal Shock (PTS) scenarios. The benchmark deals with the injection of the relatively cold Emergency Core Cooling (ECC) water which can induce buoyancy-driven stratification. Data obtained from the PTS experiment were compared with predictions obtained from the CFD software ANSYS CFX.

The results of the experiment and of the numerical calculations show that mixing is dominated by buoyancy effects: at higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this propagation. The ECC water falls in an almost vertical path and reaches the lower down-comer sen¬sor directly below the inlet nozzle. Therefore, density effects play an important role during natural convection with ECC injection in PWRs. CFD was able to predict well the observed flow patterns and mixing phenomena.
Keywords: ROCOM, CFD, PTS, RPV, CFX, ECC, PWR
  • Lecture (Conference)
    Fourth Research Coordination Meeting on the Application of Computational Fluid Dynamics Codes for Nuclear Power Plant Design, 08.11.2017, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-26114
Publ.-Id: 26114


Ex-situ doping and Ohmic contact formation with low contact resistance on MBE grown GeSn on Si

Prucnal, S.; Augel, L.; Schulze, J.; Fischer, I. A.; Berencén, Y.; Hübner, R.; Böttger, R.; Rebohle, L.; Skorupa, W.; Wang, M.; Voelskow, M.; Helm, M.; Zhou, S.
GeSn with quasi-direct band gap is one of the most promising semiconductor materials for light emitters integrated with CMOS technology. The equilibrium solid solubility limit (SSL) of Sn in Ge is in the range of 0.5 % and the predicted theoretical Sn concentration needed for the direct band gap formation is above 5 %. This means that GeSn with direct band gap is metastable and any related material process cannot be thermal equilibrium. Here we propose to utilize strongly non-equilibrium processing i.e. ion implantation followed by millisecond range flash lamp annealing (FLA), for doping and the formation of Ohmic contacts with low contact resistance on Ge0.95Sn0.05. The effective carrier concentration in P+ implanted Ge0.95Sn0.05 layer followed by FLA for 3 ms is above 5×10^19cm-3 with a specific contact resistance rc=4×10^-6Ωcm2. NiGe for Ohmic contact is made by Ni diffusion into GeSn during a single 3 ms long flash pulse. TEM images reveal that NiGe is polycrystalline but with an atomically sharp interface between the metal contact and GeSn. The influence of non-equilibrium processing (ion implantation and FLA) on the optical, electrical and microstructural properties of the GeSn layer grown by MBE on Si will be discussed in details.
Keywords: GeSn, MBE, doping, flash lamp annealing
  • Poster
    EMRS Fall Meeting 2017, 18.-21.09.2017, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-26113
Publ.-Id: 26113


Strategies for high doping of Ge

Prucnal, S.
One of the main obstacles towards wide application of Ge in nanoelectronics is the lack of an efficient doping method for the fabrication of heavily doped Ge layers with well controlled junction depth. In fact, n-type doping of Ge is a key bottleneck in the realization of advanced negative-channel metal-oxide-semiconductor (NMOS) devices. Here an overview of different doping techniques will be presented. Special attention will be focused on the use of ion implantation followed by flash-lamp (FLA) annealing for the fabrication of heavily doped Ge. In contrast to conventional annealing procedures, rear-side FLA leads to full recrystallization of Ge and dopant activation independently of pre-treatment. The maximum carrier concentration is well above 10^20 cm-3 for n-type and above 10^21 for p-type doping. The recrystallization mechanism and the dopant distribution during rear-side FLA are discussed in detail. In this work, we report on the strong mid-IR plasmon absorption from heavily P-doped Ge thin films and superconductivity in Ga and Al doped Ge obtained by non-equilibrium thermal processing. The mid-IR plasmon spectral response at room temperature from those samples was characterized by means of Fourier transform infrared spectroscopy. It is proven that the position of the plasmonic resonance frequency signal can be tuned as a function of the P concentration.
Keywords: Ge, flash lamp annealing, doping
  • Invited lecture (Conferences)
    EMRS Fall Meeting 2017, 18.-21.09.2017, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-26112
Publ.-Id: 26112


Influence of Nickel Catalyst Morphology on Layer-Exchange-Based Carbon Crystallisation of Ni/a-C Bilayers

Janke, D.; Hulman, M.; Wenisch, R.; Gemming, S.; Rafaja, D.; Krause, M.
Metal-induced crystallisation with layer exchange is applied on Ni/C bilayer stacks deposited by three PVD techniques on SiO2. The layer stacks were deposited at room temperature by either ion beam sputtering, direct current magnetron sputtering or high-power impulse magnetron sputtering. The influence of the Ni morphology on the layer exchange degree aLE and the resulting graphitic ordering is studied by atomic force microscopy, Rutherford backscattering spectrometry and Raman spectroscopy. The initial RMS roughness of the Ni top layer varied with the deposition technique by a factor of 20, from 0.3 to 6.1 nm.
After annealing in UHV at up to 700°C, layer exchange was observed for all samples. Still, the layer exchange degree was affected by the roughness of the initial bilayer stack. The highest value of 96% was achieved for magnetron-sputtered samples, what is by ~35% higher than for the initially roughest Ni surfaces. Raman spectroscopy showed the formation of graphitic carbon, characterised by a strong 2D line, for all three bilayer stacks. The degree of graphitic ordering increased with decreasing Ni surface roughness.
Keywords: Metal-induced crystallisation of amorphous carbon, Layer exchange, Rutherford Backscattering Spectrometry, Raman spectroscopy

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Publ.-Id: 26111


An Eulerian-Eulerian Computational Fluid Dynamic Approach to Predict the Boiling Process with New Developed Sub Models

Ding, W.; Krepper, E.; Hampel, U.
Time averaged Eulerian multiphase approaches and the heat flux partitioning method is popular to be applied in the computational fluid dynamic simulations of wall boiling especially in the forced convective boiling. In such CFD simulations, many submodels for the bubble dynamics and the implementation of the bubble dynamics into the global models are particularly important. In order to get accurate bubble dynamics, a single bubble model for nucleate boiling based on the known microlayer theory was developed. The single bubble model consideres the dynamic bubble geometry, contact angle and bubble inclination angle in flow boiling at different time periods. The model is able to show the dependency of bubble departure diameter (lift off diameter) and frequency on the different physical quantities such as heat flux, liquid properties, sub-cooling temperature, design of channel (diameter, length), mass flow rate and so on. The implementation of this developed single bubble model requires an update of the conventional nucleation site activation and heat partitioning models in time averaged Eulerian multiphase approaches. The new activation approach considers a distribution of cavity sizes and their influence on the activation temperature. The dynamics of the bubbles generated from different size cavities at the same position differ from each other. The updated heat partitioning model assumes the heat flux at the evaporative area always as constant and equal to the known feed heat flux when the boiling system is in the steady state. With help of the multiple size group (MUSIG) model and a breakup and coalesce model, the time averaged Eulerian approach could simulate the bubble size distribution in a heated pipe. With the necessary calibration of the nucleation site density the comparisons between the calculation results and the Bartolomej’s experiments demonstrate the accuracy of this approach.
Keywords: Forced convective boiling, Eulerian multi-phase approach, microlayer, cavity group activation, heat partitioning
  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal hydaulics, 04.-08.09.2017, Xi'an, China
    17th International Topical Meeting on Nuclear Reactor Thermal hydaulics

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Permalink: https://www.hzdr.de/publications/Publ-26110
Publ.-Id: 26110


A hypothesis of near critical heat flux (CHF-) based on minimum waiting time

Ding, W.; Krepper, E.; Hampel, U.
Boiling is a very efficient heat transfer mechanism with a large heat transfer coefficient and it is widely found in industrial systems. However, boiling heat transfer is limited by the critical heat flux (CHF), also termed as boiling crisis, which may lower efficiency and jeopardize safety of heat transfer systems. The latter is of particular importance for the safe operation of nuclear light water reactors. A clear understanding of the basic mechanisms leading to CHF is still lacking. In this paper a new model for the quantitative prediction of the initiation of critical heat flux is derived from the bubble dynamics and heat fluxes in nucleate boiling. It incorporates effects of mutual bubble interaction and shear stress from bulk flow. The model was successfully validated with available experimental data from literature for both pool boiling and forced convective boiling and with that it can be very widely applied, both as a stand-alone model for heat transfer system design as well as a sub-model in computational fluid dynamics (CFD).
Keywords: Critical heat flux (CHF), boiling heat transfer, pool boiling, forced convective boiling, cavity activation
  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 04.-08.09.2017, Xi'an, China
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics

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Permalink: https://www.hzdr.de/publications/Publ-26109
Publ.-Id: 26109


Bulk anaylsis of extraterrestrial samples using INAA at the research reactor FRM II

Li, X.; Leister, N.; Lierse Von Gostomski, C.; Merchel, S.; Gurlit, S.; Muszynski, A.; Szyszko, M.; Bischoff, A.
Within the framework of a TUM-Kolleg Project between the TU München and the Otto-von-Taube-Gymnasium Gauting three ordinary chondrites from Germany (Cloppenburg [1], Oldenburg (Bissel), Benthullen), three HEDs from Oman and North-West-Africa (Dhofar 1675, NWA 2690, NWA 2698), one lunar and one martian Meteorite (NWA 7986, NWA 4925) were analyzed by instrumental neutron actication analysis (INAA). In Germany the FRM II is currently the most intensive neutron source offering different irradiation facilities and high and pure thermal neutron flux for INAA. In total, 45 elements including many REEs could be determined. A clear difference between chondrites and achondrites could be observed according to the element compositions. The high Ba-concentration in all samples is probably a result of weathering [2].
The martian meterorite has a high concentration of Fe (17.2%) compared to other achondrites. The moon sample has higher concentrations of REEs, but is apparently not a rock with a KREEP-signature.
[1] Storz, J. et al., this meeting. [2] Stelzner, T. et al., (1999) MAPS 34, 787-794.
Keywords: AMS, meteorite, REE, INAA, ICP-MS
  • Poster
    Paneth-Kolloquium, 10.-13.10.2017, Nördlingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26108
Publ.-Id: 26108


Photochemical Reduction of Non-fluorescent Tris(carbonato)uranyl(VI) Complex

Takao, K.; Tsushima, S.ORC
A uranyl ion usually shows characteristic green emission and photochemical reactions under UV irradiation, while tris(carbonato)uranyl(VI) complex is known to be exceptionally inert because of strong quenching through the bound carbonates. In this study, we report that tris(carbonato)uranyl(VI) was immediately reduced to the corresponding uranyl(V) species under presence of tetrahydroborate and UV irradiation.
  • Lecture (Conference)
    The 67th Conference of Japan Society of Coordination Chemistry, 16.-18.09.2017, Sapporo, Japan

Permalink: https://www.hzdr.de/publications/Publ-26106
Publ.-Id: 26106


Computational study on the interaction between Eu(III) and calmodulin

Tsushima, S.ORC; Mochizuki, Y.; Komeiji, Y.; Takao, K.
there is no abstract
  • Lecture (Conference)
    Atomic Energy Society of Japan 2017 Fall Meeting, 13.-15.09.2017, Sapporo, Japan

Permalink: https://www.hzdr.de/publications/Publ-26105
Publ.-Id: 26105


Theoretical study on Calmodulin binding with Ca(II) and Eu(III) ions

Tsushima, S.ORC; Mochizuki, Y.; Komeiji, Y.; Okuwaki, K.; Abe, T.; Mori, H.; Tanaka, S.
there is no abstract
  • Lecture (Conference)
    The 78th Japan Society of Applied Physics Meeting, 05.-08.09.2017, Fukuoka, Japan

Permalink: https://www.hzdr.de/publications/Publ-26104
Publ.-Id: 26104


Cloppenburg (H4-5) – first results of a new find

Storz, J.; Bischoff, A.; Degering, D.; Ebert, S.; Heinlein, D.; Jull, T.; Kontul, I.; Li., X.; Merchel, S.; Oberst, J.; Ott, U.; Pack, A.; Peters, S.; Petö, M. K.; Rugel, G.
The Cloppenburg meteorite of 141 g was found March 15, 2017 by the facility manager of a school while collecting rocks for the school garden. The rock with a mean density of (3.33 ± 0.03) g/cm3 is a brecciated H-group ordinary chondrite (H4-5) with mean olivine and low-Ca pyroxene of Fa18.5±0.3 and Fs16.4±0.6, respectively. The breccia containing shock veins is weakly shocked (S3) and heavily weathered (W3). The occurrence of vivianite, the oxygen isotopes, and the Ba-enrichment (by INAA) indicate strong weathering in a very wet environment. Radionuclide data evaluation is still ongoing: Accelerator mass spectrometry (AMS) of 14C, will reveal the terrestrial age. An upper limit of the terrestrial age is yet set by low-level gamma-spectrometry in the Felsenkeller underground lab. No 22Na (t1/2=2.6 a) nor 44Ti (t1/2=59 a) could been detected within a counting time of 27 days, whereas 26Al (t1/2=0.7 Ma) was clearly identified. AMS of 10Be (t1/2=1.4 Ma) of ~18 dpm/kg confirms the high cosmic ray exposure age (CRE age) of (7.5 ± 0.4) Ma from noble gas mass spectrometry.
Keywords: AMS, cosmogenic nuclide, mass spectrometry, gamma-spectrometry, INAA
  • Poster
    Paneth-Kolloquium, 11.-13.10.2017, Nördlingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26103
Publ.-Id: 26103


Investigation of bioreactors by instrumented flow-following sensor particles

Reinecke, S.; Hampel, U.
Instrumented flow-following sensor particles have been developed for investigation of hydrodynamic and biochemical processes chemical reactors and bioreactors, where standard measurement techniques are not applicable. The sensor particles allow autonomous long-term measurement of spatially distributed process parameters in the chemically and mechanically harsh environments of agitated industrial vessels. Each sensor particle comprises of an on-board measurement electronics that logs the signals of the embedded sensors. A buoyancy control unit enables automated taring to achieve neutral buoyancy of the sensor particles. Moreover, controlled floating of the sensor particles is possible to expose them for recovery from the fluid surface. The paper presents exemplary results from tests in an air-water column reactor, a pilot biogas digester and a waste water treatment plant.
Keywords: sensor particle, autonomous sensor, flow follower, hydrodynamics, bioreactor
  • Contribution to proceedings
    Sensor 2017, 30.05.-01.06.2017, Nürnberg, Deutschland
  • Lecture (Conference)
    Sensor 2017, 30.05.-01.06.2017, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26102
Publ.-Id: 26102


The 2017 Magnetism Roadmap

Sander, D.; Valenzuela, S. O.; Makarov, D.; Marrows, C. H.; Fullerton, E. E.; Fischer, P.; McCord, J.; Vavassori, P.; Mangin, S.; Pirro, P.; Hillebrands, B.; Kent, A. D.; Jungwirth, T.; Gutfleisch, O.; Kim, C. G.; Berger, A.
Building upon the success and relevance of the 2014 Magnetism Roadmap, this 2017 Magnetism Roadmap edition follows a similar general layout, even if its focus is naturally shifted, and a different group of experts and, thus, viewpoints are being collected and presented. More importantly, key developments have changed the research landscape in very relevant ways, so that a novel view onto some of the most crucial developments is warranted, and thus, this 2017 Magnetism Roadmap article is a timely endeavour. The change in landscape is hereby not exclusively scientific, but also reflects the magnetism related industrial application portfolio. Specifically, Hard Disk Drive technology, which still dominates digital storage and will continue to do so for many years, if not decades, has now limited its footprint in the scientific and research community, whereas significantly growing interest in magnetism and magnetic materials in relation to energy applications is noticeable, and other technological fields are emerging as well. Also, more and more work is occurring in which complex topologies of magnetically ordered states are being explored, hereby aiming at a technological utilization of the very theoretical concepts that were recognised by the 2016 Nobel Prize in Physics. Given this somewhat shifted scenario, it seemed appropriate to select topics for this roadmap article that represent the three core pillars of magnetism, namely magnetic materials, magnetic phenomena and associated characterization techniques, as well as applications of magnetism. While many of the contributions in this Roadmap have clearly overlapping relevance in all three fields, their relative focus is mostly associated to one of the three pillars. In this way, the interconnecting roles of having suitable magnetic materials, understanding (and being able to characterize) the underlying physics of their behaviour and utilizing them for applications and devices is well illustrated, thus giving an accurate snapshot of the world of magnetism in 2017. The article consists of 14 sections, each written by an expert in the field and addressing a specific subject on two pages. Evidently, the depth at which each contribution can describe the subject matter is limited and a full review of their statuses, advances, challenges and perspectives cannot be fully accomplished. Also, magnetism, as a vibrant research field, is too diverse, so a number of areas will not be adequately represented here, leaving space for further roadmap editions in the future. However, this 2017 Magnetism Roadmap article can provide a frame that will enable the reader to judge where each subject and magnetism research field stands overall today and which directions it might take in the foreseeable future. The first material focused pillar of the 2017 Magnetism Roadmap contains five articles, which address the questions of atomic scale confinement, 2D, curved and topological magnetic materials, as well as materials exhibiting unconventional magnetic phase transitions. The second pillar also has five contributions, which are devoted to advances in magnetic characterization, magneto-optics and magneto-plasmonics, ultrafast magnetization dynamics and magnonic transport. The final and application focused pillar has four contributions, which present non-volatile memory technology, antiferromagnetic spintronics, as well as magnet technology for energy and bio-related applications. As a whole, the 2017 Magnetism Roadmap article, just as with its 2014 predecessor, is intended to act as a reference point and guideline for emerging research directions in modern magnetism.
Keywords: magnetism, roadmap, magnetic materials, magneto-optics, spintronics, magnonics, magnetic memory

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Permalink: https://www.hzdr.de/publications/Publ-26101
Publ.-Id: 26101


Mesoscale Dzyaloshinskii-Moriya interaction: geometrical tailoring of the magnetochirality

Volkov, O. M.; Sheka, D. D.; Kravchuk, V. P.; Gaididei, Y.; Rößler, U. K.; Faßbender, J.; Makarov, D.
Crystals with broken inversion symmetry can host fundamentally appealing and technologically relevant periodical or localized chiral magnetic textures. The type of the texture as well as its magnetochiral properties are determined by the intrinsic Dzyaloshinskii-Moriya interaction (DMI), which is a material property and can hardly be changed. Here we put forth a method to create new artificial chiral nanoscale objects with tunable magnetochiral properties from standard magnetic materials by using geometrical manipulations. We introduce a mesoscale Dzyaloshinskii-Moriya interaction that combines the intrinsic spin-orbit- and extrinsic curvature-driven DMI terms and depends both on the material and geometrical parameters. The vector of the mesoscale DMI determines magnetochiral properties of any curved magnetic system with broken inversion symmetry. The strength and orientation of this vector can be changed by properly choosing the geometry. For a specific example of nanosized magnetic helix, the same material system with different geometrical parameters can acquire one of three zero-temperature magnetic phases, namely, phase with a quasitangential magnetization state, phase with a periodical state and one intermediate phase with a periodical domain wall state. The difference between equilibrium magnetization states for magnetic nanohelices with opposite geometrical chiralities put forth on a new simple measuring method of the DMI constant. Our approach paves the way towards the realization of a new class of nanoscale spintronic and spinorbitronic devices with the geometrically tunable magnetochirality.
Keywords: curvilinear magnetism, curved magnetic nanowires, micromagnetism

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Permalink: https://www.hzdr.de/publications/Publ-26100
Publ.-Id: 26100


Magnetic coupling phenomena in curved nanomagnets

Makarov, D.
Magnetic curvilinear objects possess new fundamental properties originating from the curvature-driven effects, leading to magnetochiral effects and topologically induced magnetization patterns. Recently, it was theoretically predicted that these effects come from the exchange-induced curvilinear interactions like anisotropy-like and chiral-like parts [R. Streubel et al., Magnetism in curved geometries (topical review), Journal of Physics D: Applied Physics 49 p. 363001 (2016)]. These recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this talk.
Keywords: curved magnetic thin films, curvilinear magnetism
  • Invited lecture (Conferences)
    Magnetic Coupling in Nanostructured Materials, 23.-25.10.2017, Rome, Italy

Permalink: https://www.hzdr.de/publications/Publ-26098
Publ.-Id: 26098


Spintronics of thin film granular antiferromagnets

Makarov, D.
Antiferromagnets have the potential to revolutionize spintronics due to their inherently magnetic-field stable magnetic order and high-frequency operation. There are already great advances in the field especially when bulk antiferromagnets are considered. The application potential of antiferromagnets can be explored in full only if they will be prepared in the way to be compatible with a conventional microelectronic processing. This necessarily requires the use of (i) thin film antiferromagnets and (ii) discovery of methods to address the order parameter and its modifications all-electrically.
With respect to the first challenge it is necessary to understand modifications of the magnetic properties and magneto-electric responses of thin film antiferromagnets with respect to their bulk counterparts. Typically, thin films possess grainy morphology. Hence, to determine their application potential, questions regarding the change of the intergranular exchange, criticality behavior and switching of the order parameter need to be answered. This topic I will illustrate on the specific example of thin film magnetoelectric collinear antiferromagnet α-Cr2O3 studied using zero-offset Hall magnetometry and NV microscopy [1].
To address the second challenge it is required to develop transport-based techniques to harness the responses of thin film antiferromagnets. This task is difficult as minute uncompensated surface magnetization of antiferromagnets needs to be detected, which imposes strict requirements to the sensitivity of the method. I will outline our developments of zero-offset anomalous Hall magnetometry [2] applied to study the physics of conventional metallic IrMn and insulating magnetoelectric Cr2O3 antiferromagnets.
The fundamental understanding of the magnetic microstructure of magnetoelectric α-Cr2O3 thin films and the possibility to read-out its antiferromagnetic order parameter all-electrically enabled the entirely new recording concept where a magnetoelectric memory cell can be addressed without using a ferromagnet. With this approach, we opened an appealing field of purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) [1]. The key performance parameters of the Cr2O3 based AF-MERAM will be highlighted.

[1] T. Kosub, M. Kopte, R. Hühne, P. Appel, B. Shields, P. Maletinsky, R. Hübner, M. O. Liedke, J. Fassbender, O. G. Schmidt, and D. Makarov, “Purely antiferromagnetic magnetoelectric random access memory”. Nature Communications 8, 13985 (2017).
[2] T. Kosub, M. Kopte, F. Radu, O. G. Schmidt, and D. Makarov, “All-Electric access to the magnetic-field-invariant magnetization of antiferromagnets”. Phys. Rev. Lett. 115, 097201 (2015).
Keywords: antiferromagnetic spintronics, magnetoelectric Memory
  • Invited lecture (Conferences)
    Workshop on antiferromagnetic spintronics, 25.-27.10.2017, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-26097
Publ.-Id: 26097


Electronic proprioception

Makarov, D.
Augmented reality gadgets are becoming common for our information intensive society assisting us to acquire and process the data. Although impressive in the realization and demonstrations, the obvious drawback of the state-of-the-art augmented and virtual reality devices relying on optical detection systems is their bulkiness, energy inefficiency and the stringent requirement for an operator to be at the line of sight of the device.
We envision that prospective augmented reality systems will strongly benefit from the recent developments in compliant on-skin electronics. The fabrication of highly conformable gadgets requires the realization of the electronic replica of the exteroceptive sensory system of humans as well as calls for the acquiring new perception skills beyond those prescribed by the evolution. The first crucial step towards the realization of this vision was accomplished with the development of interactive magnetosensitive skins [1-4].
Here, we present the first on-skin gadgets, which replicate our natural proprioceptive sensory ability of detecting the motion. Relying on this magnetically enabled electronic proprioception, we visualize the bodily motion and demonstrate the touchless manipulation of virtual objects for augmented reality systems. Those highly conformable interactive devices possess great potential to extend the portfolio of tasks, which can be performed in virtual or augmented reality. The integration of gadgets in imperceptible electronic skins will open not only exciting possibilities for business or gaming industry but is also beneficial for safety and security applications, where the somatic manipulation of objects, e.g. turning regulation knobs located in a restricted environment is undesirable or even prohibited.

1. M. Melzer et al., Nature Commun. 6, 6080 (2015).
2. M. Melzer et al., Adv. Mater. 27, 1274 (2015).
3. N. Münzenrieder et al., Adv. Electron. Mater. 2, 1600188 (2016).
4. D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
Keywords: magnetic field sensors, flexible electronics
  • Invited lecture (Conferences)
    NanoBioSensor Conference, 04.-05.09.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26096
Publ.-Id: 26096


H-T phase diagram of solid oxygen

Nomura, T.; Matsuda, Y. H.; Kobayashi, T. C.
The comprehensive magnetic field–temperature (H-T) phase diagram of solid oxygen including the θ phase is discussed in the context of the ultrahigh-field measurement and the magnetocaloric effect (MCE) measurement. The problems originating from the short duration of the pulse field, nonequilibrium conditions and MCEs, are pointed out and dealt with. The obtained phase diagram manifests the entropy relation between the phases as Sθ ∼ Sα < Sβ << Sγ

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Permalink: https://www.hzdr.de/publications/Publ-26095
Publ.-Id: 26095


Investigation of the temperature in dense carbon near the solid-liquid phase transition between 100 GPa and 200 GPa with spectrally resolved X-ray scattering

Helfrich, J.; Vorberger, J.; Frydrych, S.; Schaumann, G.; Gericke, D. O.; Ravasio, A.; Gauthier, M.; Fletcher, L. B.; Nagler, B.; Barbrel, B.; Bachmann, B.; Gamboa, E. J.; Göde, S.; Granados, E.; Lee, H. J.; Neumayer, P.; Schumaker, W.; Döppner, T.; Falcone, R. W.; Glenzer, S. H.; Roth, M.; Kraus, D.
We present experiments investigating dense carbon at pressures between 100 GPa and 200 GPa and temperatures between 5 000K and 15 000 K. High-pressure samples with different temperatures were created by laser-driven shock compression of graphite and varying the initial density from 1.53 g/cm3 to 2.21 g/cm3 and the drive laser intensity from 7.1TW/cm2 to 14.2TW/cm2. In order to deduce temperatures, spectrally resolved X-ray scattering was applied to determine ion-ion structure factors at a scattering vector of k = 4.12 · 1010 m−1, which shows high sensitivity to temperature for the investigated sample conditions. After comparison to corresponding DFT-MD simulations, we were able to assign each structure factor a temperature and use these results to test several theoretical predictions for the melting line of carbon at high pressures.
Keywords: warm dense matter, warm dense carbon, melting line, high pressure fluid, high pressure solid, x-ray scattering, high power laser, first principle simulations

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  • Secondary publication expected from 01.07.2020

Permalink: https://www.hzdr.de/publications/Publ-26094
Publ.-Id: 26094


Retention and multiphase transformation of selenium oxyanions during the formation of magnetite via ferrous hydroxide and green rust

Börsig, N.; Scheinost, A. C.; Shaw, S.; Schild, D.; Neumann, T.
Environmental and health hazards of the trace element Se are mainly related to the presence of highly mobile Se oxyanion species (oxidation states +4 and +6). In this study, we investigate the immobilization of dissolved Se oxyanions during the formation process of magnetite by the progressive oxidation of an alkaline, anoxic Fe2+ system (pH 9.2). Up to initial concentrations of c(Se)0 = 10-3 mol/L (m/V ratio = 3.4 g/L), logRd values of xxxx demonstrate a strong retention of Se oxyanions during this mineral formation process. This Se immobilization is due to the reduction of Se(IV) or Se(VI), resulting in the precipitation of sparingly soluble Se compounds. By XRD analysis, these Se compounds were identified as crystalline elemental Se(0) that occurred in all coprecipitation products after the completed magnetite formation. The time-resolved analysis of the Se retention during the magnetite formation and detailed spectroscopic analyses (XPS, XAS) of the involved solid phases showed that the reduction takes place under the anoxic conditions in the early phase of the coprecipitation process by the interaction with iron(II) hydroxide and green rust. Both minerals represent the primary Fe(II)-containing precipitation products in the aquatic Fe2+ system and the precursor phases of the later formed magnetite. Spectroscopic and electron microscopic analysis prove that this early Se interaction leads to the formation of a nanoparticulate iron selenide phase [FeSe], which is oxidized and transformed into trigonal gray elemental Se during the progressive oxidation of the system. Regarding the retention behavior of Se, it is irrelevant whether the oxidation of the meta-stable iron oxide phases leads to the formation of magnetite only or also to other iron oxide phases like goethite. This reductive precipitation of Se induced by an interaction with metastable Fe(II)-containing iron oxide minerals should affect the mobility of Se oxyanions in contaminated environments, including the behavior of 79Se in the near-field of HLW repositories.
Keywords: selenite, selenate, selenide, iron oxide, reduction, oxidation, precipitation, immobilization, XPS, XAS, EXAFS

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Permalink: https://www.hzdr.de/publications/Publ-26093
Publ.-Id: 26093


Permutation-blocking path-integral Monte Carlo approach to the static density response of the warm dense electron gas

Dornheim, T.; Groth, S.; Vorberger, J.; Bonitz, M.
The static density response of the uniform electron gas is of fundamental importance for numerous applications.
Here we employ the recently developed ab initio permutation blocking path integral Monte Carlo (PB-PIMC) technique [T. Dornheim et al., New J. Phys. 17, 073017 (2015)] to carry out extensive simulations of the harmonically perturbed electron gas at warm dense matter conditions. In particular, we investigate in detail the validity of linear response theory and demonstrate that PB-PIMC allows us to obtain highly accurate results for the static density response function and, thus, the static local field correction. A comparison with dielectric approximations to our new ab initio data reveals the need for an exact treatment of correlations. Finally, we consider a superposition of multiple perturbations and discuss the implications for the calculation of the static response function.
Keywords: warm dense matter, quantum monte carlo, response function, electron gas, fermion sign problem, linear response
  • Physical Review E 96(2017), 023203

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Permalink: https://www.hzdr.de/publications/Publ-26091
Publ.-Id: 26091


Optical contrast formation in ta-C films by ion implantation

Berova, M.; Sandulov, M.; Tsvetkova, T.; Szekeres, A.; Terziyska, P.; Kitova, S.; Böttger, R.; Bischoff, L.
Tetrahedral amorphous carbon (ta-C) thin films (d ~ 40 nm), deposited by filtered cathodic vacuum arc (FCVA) method, have been implanted with Ga+ ions with energy 20 keV and ion fluences 3xE14 and 3xE15 cm-2. The implantation induced modification of the films structure is reflected in a considerable change of their optical properties, best manifested by a significant shift of the optical absorption edge to lower photon energies as obtained from optical measurements. This shift is accompanied by a considerable increase of the absorption coefficient in the photon energy range (0.5 ÷ 3.0 eV). The observed effects could be attributed both to additional defect generation and increased graphitization, as well as by gallium colloids formation. The optical contrast thus obtained (between implanted and unimplanted film material) could be of use in the area of high-density optical data storage using focused Ga+ ion beams.
Keywords: ta-C films, Ga implantation, optical properties
  • Revue Roumaine de Chimie 62(2017)10, 761-765

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Permalink: https://www.hzdr.de/publications/Publ-26090
Publ.-Id: 26090


CFD-simulation of different bubbly flow situations applying the Euler-Euler framework

Krepper, E.; Lucas, D.; Rzehak, R.
A widely used approach to model two-phase bubbly flows for industrial applications is the Eulerian two-fluid framework of interpenetrating continua. The loss of details caused by the averaging procedure has to be compensated by consideration of additional closure relations. These concern the momentum exchange between the phases, the effect of the bubbles on liquid turbulence and bubble breakup & coalescence. A set of best available sub models was assembled (Rzehak and Krepper, 2013, 2015). To ensure the predictive capabilities it has to be shown that this model framework is able to describe different flow situations without any changes of model parameters.
The present contribution starts with validation work on upward turbulent bubbly flow in a vertical tube at the MTLoop facility using the wiremesh technique. A second step is the extension to counter-current and co-current downward flow at ROFEX using fast X-Ray tomography (Krepper et al. 2016). Both facilities were operated in Helmholtz - Zentrum Dresden-Rossendorf. Data on the cross sectional distribution of gas volume fraction, of gas and liquid velocity and on bubble size distributions were gained.
The presentation shows the capability of an unified framework of closure relationships to describe different flow situations.
Keywords: CFD, momentum exchange, bubble induced turbulence, fixed polydispersed flow
  • Lecture (Conference)
    The 3rd International Conference on Numerical Methods in Multiphase Flows, ICNMMF-III, 26.-29.06.2017, Tokyo, Japan

Permalink: https://www.hzdr.de/publications/Publ-26089
Publ.-Id: 26089


CFD analysis on experiments of bubbly flow in a tube with an obstacle

Krepper, E.; Neumann, M.; Lucas, D.
Two phase adiabatic air/water flow in a vertical tube with an inner diameter of 54 mm equipped with an inner obstacle was investigated. Experiments are conducted for a wide range of superficial gas and liquid velocities in bubbly flow regime. Flow obstacles, namely a ring shaped diaphragm and a half-moon shaped diaphragm, are used for generation of three-dimensional flow fields. Besides conventional measurement techniques an ultrafast X-ray tomography scanner ROFEX, which was developed by HZDR, are applied. ROFEX determines gas distributions, bubble velocities and bubble sizes (Hampel et al. 2013, 2016).
The experiments were used to analyze the capability of the actual CFD based on the Euler/Eulerian approach. The CFD calculations were performed as pre-test simulations. Measured results for half-moon shaped diaphragm tests were available short before publishing the manuscript and shown with the calculations. Most of the values and at least the tendencies could be predicted with good agreement to measurements. Reasons for deviations are discussed in the paper.
CFD simulation enables the investigation of single components of the model approach. So the distribution of the bubble forces and the strength and location of single breakup&coalescence mechanisms can be analyzed and checked for plausibility.
Keywords: bubbly flow, experiments, CFD, momentum exchange, bubble induced turbulence, bubble breakup & coalescence
  • Contribution to proceedings
    The 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi'an, China
  • Lecture (Conference)
    The 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi'an, China

Permalink: https://www.hzdr.de/publications/Publ-26088
Publ.-Id: 26088


Concepts of CFD modelling of boiling towards CHF

Krepper, E.; Ding, W.
Boiling is an effective heat transfer mechanism which plays an important role in many industrial applications. The heat transfer capability is limited by the critical heat flux (CHF). The conditions for CFX have to be avoided in any cases. The simulation of these not yet fully understood phenomena has not yet reached an acceptable maturity.
The presentation describes actual concepts of simulation of boiling beginning with the heat flux partitioning approach. In recent developments the bubble size distribution was considered. Concepts for describing CHF are presented.
Keywords: Boiling, CFD, Heat flux partitioning, bubble population balance, critical heat flux
  • Lecture (Conference)
    28th Meeting of the German CFD Network of Competence, 07.03.2017, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26087
Publ.-Id: 26087


Substitution mechanisms in In, Au, and Cu-bearing sphalerites studied by X-ray absorption spectroscopy of synthetic and natural minerals

Filimonova, O. N.; Trigub, A. L.; Tonkacheev, D. E.; Nickolsky, M. S.; Kvashnina, K. O.; Chareev, D. A.; Chaplygin, I. V.; Kovalchuk, E. V.; Lafuerza, S.; Tagirov, B. R.
Processing of Zn ore accounts for >95% of production of In - a "critical" metal which is widely used in the high-tech electronics. The main source of In is sphalerite (Zn, Fe)S which also can host industrial concentrations of Au. Here we use X-ray absorption spectroscopy to investigate the coupled chemistry of In and Au in synthetic sphalerite crystals - analogues of natural minerals. The concentrations of In and Au were found to correlate with each other and reached 0.5 wt% in crystals synthesized at 850 °C. Both metals are homogeneously distributed within the sphalerite matrix. However, their positions within the mineral are different. In accord with X-ray absorption near edge structure (XANES) spectroscopy the formal oxidation state of these elements is +3 (In) and +1 (Au). Analysis of extended X-ray absorption fine structure (EXAFS) spectra revealed that In replaces Zn in the structure of sphalerite. The In-ligand distance increases by 0.12 Å and 0.09-0.10 Å for the 1st and 2nd coordination spheres, respectively, in comparison with pure ZnS. The In-S distance in the 3rd coordination sphere is close to the one of pure sphalerite. The In K-edge and Au L3-edge XANES and EXAFS spectra suggest that there is no In-Au clustering. Gold in sphalerite is coordinated with 2.5±0.3 S atoms at Au-S distance of 2.35±0.01 Å in the 1st coordination sphere, whereas distant coordination spheres have disordered nature.
Our data suggest that at least two different forms of Au are present in sphalerite. At high Au concentrations (0.03-0.5 wt%) the nanosized Au2S clusters predominate, probably with small admixture of the Au solid solution characterized by higher Au-S distance. Alike Au, the other 1st group metals (Me) Cu and Ag, which often are present in high (tenths ppm to wt%) concentrations in sphalerite, can form nanosized Me-S clusters with only traces (ppm level) of metal in the solid solution state.

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Permalink: https://www.hzdr.de/publications/Publ-26086
Publ.-Id: 26086


Radioimmunkonjugate für die theragnostische Anwendung an Prostata-Stammzellantigen-exprimierenden Tumoren

Oertel, F.; Arndt, C.; Feldmann, A.; Bergmann, R.; Steinbach, J.; Pietzsch, H.-J.; Bachmann, M.
Ziel: Das Prostata-Stammzellantigen (PSCA) wird auf der Zelloberfläche von über 80% der Prostatatumore (PCa) und deren Knochenmetastasen exprimiert. Aus diesem Grund wird es häufig als Zielstruktur sowohl für die Radioimmuntherapie (RIT) als auch für molekulare Bildgebungstechniken von PCa in der Nuklearmedizin (Positronen-Emissions-Tomographie (PET) und Einzelphotonen-Emissionscomputertomographie (SPECT)) verwendet. Für die jeweiligen Anwendungsgebiete wurden Radioimmunkonjugate basierend auf monoklonalen anti-PSCA-Antikörpern (mAk, 150 kDa) und von diesen abgeleitete Einzelkettenantikörperfragmente („single-chain Fragment variable“ (scFv), 35 kDa) hergestellt. In Kombination sollen diese Radioimmunkonjugaten als therapeutisches und diagnostisches Instrument für PSCA-positive PCa Anwendung finden.
Methoden und Ergebnisse: Zwei unterschiedliche anti-PSCA mAk-Klone, RD1 und RD2 genannt, sowie davon abgeleitete scFvs wurden hergestellt, über Affinitätschromatographie gereinigt und deren Bindungseigenschaften an PSCA-positiven PC3-Zellen mittels Durchflusszytometrie ermittelt. Die unmarkierten mAk-Klone RD1 und RD2 zeigten hohe Affinitäten, mit Dissoziationskonstanten von 10 und 6 nM. Für die scFvs von RD1 und RD2 wurden geringere Affinitäten von 170 und 98 nM bestimmt. Die beiden mAk-Klone wurden anschließend mit dem bifunktionellen Chelator p-SCN-Bn-CHX-A’’-DTPA, die scFv-Antikörper hingegen mit p-SCN-Bn-NOTA konjugiert. Für alle Konstrukte wurde mittels MALDI-TOF-Massenspektrometrie eine durchschnittliche Anzahl von drei Chelator-Einheiten je Antikörpermolekül gemessen. Anschließend wurden die mAk-Konjugate für eine mögliche RIT-Anwendung mit Lutetium-177 und die scFv-Konjugate für eine mögliche PET-Bildgebung mit Kupfer-64 radiomarkiert. Des Weiteren wurden scFv-Antikörper auch direkt mit Technetium-99m mit Hilfe eines Tricarbonyl-Präkursor an ihrem Hexahistidin-Tag für eine mögliche SPECT-Bildgebung markiert. Für alle radiomarkierten Konjugate wurde eine radiochemische Reinheit von über 95% (radio-Dünnschichtchromatographie) erzielt. Nachfolgende In-vitro-Studien an PC3-PSCA-Zellen zeigten, dass die Bindungseigenschaften zum PSCA erhalten bleiben.
Ausblick: An entsprechenden Tumormaus-Modellen wird gegenwärtig geprüft, ob die positiven in-vitro Resultate für die hergestellten Radioimmunkonjugate bestätigt werden können.
  • Poster
    GdCh Wissenschaftsforum Chemie 2017, 10.-14.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26085
Publ.-Id: 26085


Radioimmunoconjugates for theragnostics of Prostate Stem Cell Antigen (PSCA)-expressing tumors

Oertel, F.; Arndt, C.; Feldmann, A.; Bergmann, R.; Steinbach, J.; Bachmann, M.; Pietzsch, H.-J.
Aim: Advances in molecular engineering have led to the development of a multiplicity of antibody fragments with variations in molecular size. With respect to tumor targeting, the molecular size evidently determines the tumor uptake and pharmacokinetics. Consequently, they are proposed for different applications: small radiolabeled antibody fragments, such as single-chain variable fragments (scFv, 25-35 kDa) for tumor imaging and large full-size monoclonal antibodies (mAbs, 150 kDa) for radioimmunotherapy. Here, mAbs and thereof derived scFvs were produced that are directed against the prostate stem cell antigen (PSCA). Due to its overexpression on the surface of various tumor types, including prostate cancer and its metastases, it is proposed as a promising tumor target structure. Both antibody-based targeting molecules might provide a combinatory tool for theranostics of PSCA-positive prostate cancer.

Methods: In this study, two different anti-PSCA mAb clones, RD1 and RD2, as well as their respective anti-PSCA scFvs were produced and compared with regard to their binding properties towards PSCA, using flow cytometry analysis. The anti-PSCA mAbs were conjugated with the chelating agent p-SCN-CHX-A’’-DTPA, measured by MALDI-TOF, and subsequently radiolabeled with lutetium-177, whereas the scFvs were radiolabeled with technetium-99m on their histidine-tag. Thereafter, all radiolabeled conjugates were characterized by thin-layer chromatography, and regarding binding properties on PC3-PSCA cells in vitro.

Results: The non-radiolabeled anti-PSCA mAbs RD1 and RD2 showed a high affinity, with dissociation constants of 10 and 6 nM, respectively. The corresponding scFvs of RD1 and RD2 exhibit a lower affinity, with Kd-values of 170 and 98 nM. Both full mAbs were conjugated with about three CHX-A’’-DTPA. This conjugation had no influence on binding affinity towards the PSCA. Subsequent radiolabeling of the mAb-conjugates and scFvs could be performed with high radiochemical purity (> 95%) with preserving their binding properties to the PSCA.

Conclusion: Full-size mAbs and scFvs that target the tumor antigen PSCA were successfully produced and radiolabeled. The in vitro characterization showed promising results to proceed with studies on tumor mouse models.
  • Poster
    The 22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), 14.-19.05.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26084
Publ.-Id: 26084


THz-driven dynamics probed by time-resolved ARPES – the high repetition rate opportunity

Deinert, J.-C.ORC; Green, B. W.; Kovalev, S.; Gensch, M.
Terahertz radiation offers unique control of low-energy excitations in matter. Fundamental modes, such as molecular rotations, lattice vibrations, electron and ion motion or spin precession can be coherently controlled on an ultrafast timescale, while parasitic electronic excitations are suppressed, because of the low THz photon energy.
The THz-induced effects, e.g. phase transitions in solids or modifications of chemical reactions are intrinsically connected to changes in the electronic structure of the material. The natural way to directly probe these changes is time- and angle-resolved photoelectron spectroscopy (tr-ARPES).
The main challenges which have impeded the experimental realization are:
availability of high field and high repetition rate THz source
knowledge and control of interaction of photo- electrons with THz field (“streaking”)
Accelerator-based THz sources like FLASH and TELBE provide ideal conditions for establishing feasibility and dynamic range of THz-pump tr-ARPES.
Keywords: Terahertz, Photoelectron Spectroscopy, pump-probe, ultrafast, condensed matter
  • Poster
    Future of science at FLASH - Opportunities with a cw XUV and soft X-ray FEL, 25.09.2017, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26083
Publ.-Id: 26083


Effective proton-neutron interaction near the drip line from unbound states in 25,26F

Vandebrouck, M.; Lepailleur, A.; Sorlin, O.; Aumann, T.; Caesar, C.; Holl, M.; Panin, V.; Wamers, F.; Stroberg, S. R.; Holt, J. D.; de Oliveira Santos, F.; Alvarez-Pol, H.; Atar, L.; Avdeichikov, V.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Bertulani, C. A.; Bogner, S. K.; Boillos, J. M.; Boretzky, K.; Borge, M. J. G.; Caamano, M.; Casarejos, E.; Catford, W.; Cederkall, J.; Chartier, M.; Chulkov, L.; Cortina-Gil, D.; Cravo, E.; Crespo, R.; Datta Pramanik, U.; Diaz Fernandez, P.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; Fraile, L. M.; Freer, M.; Galaviz, D.; Geissel, H.; Gernhäuser, R.; Gibelin, J.; Golubev, P.; Göbel, K.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Hergert, H.; 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, J.; Marques, F. M.; Movsesyan, A.; Nacher, E.; Najafi, M.; Nikolskii, E.; Nilsson, T.; Nociforo, C.; Paschalis, S.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Reifarth, R.; Ribeiro, G.; Rigollet, C.; Röder, M.; Rossi, D.; Savran, D.; Scheit, H.; Schwenk, A.; Simon, H.; Syndikus, I.; Taylor, J. T.; Tengblad, O.; Thies, R.; Togano, Y.; Velho, P.; Volkov, V.; Wagner, A.; Weick, H.; Wheldon, C.; Wilson, G.; Winfield, J. S.; Woods, P.; Yakorev, D.; Zhukov, M.; Zilges, A.; Zuber, K.
Odd-odd nuclei, around doubly closed shells, have been extensively used to study proton-neutron interactions. However, the evolution of these interactions as a function of the binding energy, ultimately when nuclei become unbound, is poorly known. The 26F nucleus, composed of a deeply bound p0d5=2 proton and an unbound n0d3=2 neutron on top of an 24O core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a Jp = 1+ - 4+1 multiplet, whose energies must be determined to study the influence of the proximity of the continuum on the corresponding proton-neutron interaction. The Jp = 1+1 ; 2+1 ; 4+1 bound states have been determined, and only a clear identification of the Jp = 3+ 1 is missing.
Keywords: Coulomb dissociation radioactive beam

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Permalink: https://www.hzdr.de/publications/Publ-26082
Publ.-Id: 26082


Bio-recycling of metals: Recycling of technical products using biological applications

Pollmann, K.; Kutschke, S.; Matys, S.; Raff, J.; Hlawacek, G.; Lederer, F. L.
The increasing demand of different metals as a consequence of the development of new technologies, especially in the so called “low carbon technologies” require the development of innovative technologies that enable an environmentally friendly metal recovery. Current recycling rates are very low due to the increasing complexicity of products and the low content of certain critical elements. Therefore efforts have to be done on efficient recycling methodologies in order to enable a circular economy. Modern biotechnologies can contribute to solve some of the problems related to metal recycling. These approaches use natural properties of organisms, bio-compounds, and biomolecules to interact with minerals, materials, metals, or metal ions such as surface attachment, mineral dissolution, transformation, and metal complexation. The article presents some recent developments in the fields of bioleaching, biosorption, bioreduction, and bioflotation and their use for metal recovery from electronic devices, waste material, and industrial effluents.
Keywords: Biohydrometallurgy, biomining, bioleaching, biosorption, bioflotation, bioreduction, metal recovery, recycling, critical metals

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Permalink: https://www.hzdr.de/publications/Publ-26081
Publ.-Id: 26081


Investigation of the superconducting gap structure in κ-(BEDT-TTF)2Cu(NCS)2 and κ-(BEDT-TTF)2Cu[N(CN)2]Br by means of thermal-conductivity measurements

Kühlmorgen, S.; Schönemann, R.; Green, E. L.; Müller, J.; Wosnitza, J.
We report temperature-dependent thermal-conductivity, κ, measurements on the layered quasi-two-dimensional organic superconductors κ-(BEDT-TTF)2Cu(NCS)2 and κ-(BEDTTTF)2Cu[N(CN)2]Br down to 160 mK. The results for κ-(BEDT-TTF)2Cu(NCS)2 may be consistent with a nodal superconducting (SC) gap structure as indicated by a nonnegligible remnant linear contribution when κ /T α T2 is extrapolated to T = 0. For κ-(BEDT-TTF)2Cu[N(CN)2]Br, contrary to expectations, higher κ values are observed in the superconducting regime as compared to the normal, high-field state evidencing a dominant phonon contribution to κ in the superconducting state. The strong increase of κ in the normal state below Tc for both samples indicates strong electron–phonon scattering. Our results highlight the need for thermal-conductivity measurements performed down to significantly lower temperatures to determine the symmetry of the SC gap.

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Permalink: https://www.hzdr.de/publications/Publ-26080
Publ.-Id: 26080


Experimental Assessment of a Flat Sandwich-Like Self-Powered Detector for Nuclear Measurements in ITER Test Blanket Modules

Raj, P.; Angelone, M.; Döring, T.; Eberhardt, K.; Fischer, U.; Klix, A.; Schwengner, R.
Neutron and gamma flux measurements in designated positions in the test blanket modules (TBM) of ITER will be important tasks during its campaigns. Investigations on self-powered detectors (SPD) - a type of flux monitors, are undertaken in the framework of an ongoing project on development of nuclear instrumentation for European ITER TBMs. This paper reports the findings of experiments performed with an SPD in flat sandwich-like geometry. A detector with vanadium emitter is chosen for preliminary studies. Its irradiation in a thermal neutron field gives a proof of the principle of flat SPDs. It is further irradiated in the mixed neutron-gamma field of a 14 MeV neutron generator and a bremsstrahlung photon field. The detector signals are
proportional to the incident fluxes, deeming it suitable for flux monitoring. Whereas both neutrons and gammas can be detected with appropriate optimization of geometries, materials and sizes of the components, the present design is more sensitive to gammas than fast neutrons. Based on the measured sensitivities of the SPD, its response under TBM conditions is predicted.
Keywords: test blanket modules, neutron flux, gamma flux monitors, elf-powered detectors

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Permalink: https://www.hzdr.de/publications/Publ-26079
Publ.-Id: 26079


Quasi-two-dimensional Fermi surfaces with localized f electrons in the layered heavy-fermion compound CePt2In7

Götze, K.; Krupko, Y.; Bruin, J. A. N.; Klotz, J.; Hinlopen, R. D. H.; Ota, S.; Hirose, Y.; Harima, H.; Settai, R.; Mccollam, A.; Sheikin, I.
We report measurements of the de Haas–van Alphen effect in the layered heavy-fermion compound CePt2In7 in high magnetic fields up to 35 T. Above an angle-dependent threshold field, we observed several de Haas–van Alphen frequencies originating from almost ideally two-dimensional Fermi surfaces. The frequencies are similar to those previously observed to develop only above a much higher field of 45 T, where a clear anomaly was detected and proposed to originate from a change in the electronic structure [M. M. Altarawneh et al., Phys. Rev. B 83, 081103 (2011)]. Our experimental results are compared with band structure calculations performed for both CePt2In7 and LaPt2In7, and the comparison suggests localized f electrons in CePt2In7. This conclusion is further supported by comparing experimentally observed Fermi surfaces in CePt2In7 and PrPt2In7, which are found to be almost identical. The measured effective masses in CePt2In7 are only moderately enhanced above the bare electron mass m0, from 2m0 to 6m0.

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Permalink: https://www.hzdr.de/publications/Publ-26078
Publ.-Id: 26078


Preparation of 18F-labeled building blocks for peptide conjugation using the "minimalist" approach

Omrane, M. A.; Zlatopolskiy, B. D.; Urusova, E.; Mamat, C.; Feni, L.; Neundorf, I.; Neumaier, B.
Recently, the “minimalist” protocol for radiofluorination was reported. This method allowed to prepare labeled probes from only [18F]F– and onium salts without base and other additives avoiding time-consuming azeotropic drying. The aim of this work was the implementation of the “minimalist” approach for the preparation of radiofluorinated building blocks via SN2. [18F]Fluoride was eluted from a QMA cartridge with an appropriate azetidinium or onium salt precursor of [18F]AFP, [18F]BFP and 5-[18F]FDR in MeOH. MeOH was evaporated at 55°C (550 mbar) within 2–3 min. MeCN was added and the resulting solutions were heated to give the corresponding 18F-labeled products. Protected 5-[18F]FDR was purified by SPE and thereafter deprotected under acidic conditions. Finally, reaction conditions for the conjugation of 5-[18F]FDR to aminooxy-functionalized peptides via chemoselective oxime ligation were optimized. [18F]F– was eluted from an anion exchange resin almost quantitatively. Under optimized conditions appropriately protected 5-[18F]FDR as well as [18F]AFP and [18F]BFP were prepared from the corresponding 3-N,N,N-trimethylammoniumalkyl(aryl)sulfonyl and azetidinium precursors in RCYs of up to 70%, 90% and 91% (determined by radio-HPLC analysis of the crude product), respectively. After SPE purification 5-[18F]FDR was obtained in 41% RCY (EOB) and excellent RCP >99% after deprotection with 1 m HCl (110 °C, 12 min) . The amount of d-ribose (60–80 μg/batch), a competitor in subsequent oxime ligation, was low enough to allow an efficient conjugation of 5-[18F]FDR with aminooxy-functionalized peptides. The corresponding conjugates were prepared in RCYs of up to 91%. The SN2 radiofluorination under “minimalist” conditions is well suited for the fast production of versatile 18F-labeled building blocks. The positively charged trimethylammonium “tag” of the 5-[18F]FDR precursor enables its simple separation from the labeled product using SPE. The prosthetic group was sufficiently pure for the subsequent labeling of peptides.
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), Dresden, 14.-19.05.2017, Dresden, Deutschland
  • Open Access Logo Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, S261
    DOI: 10.1002/jlcr.3508

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Permalink: https://www.hzdr.de/publications/Publ-26077
Publ.-Id: 26077


Evaluation of Ba/Ra Polyoxopalladates for Radiopharmaceutical Applications

Gott, M.; Yang, P.; Kortz, U.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.
Alpha particles show great promise for therapeutic applications due to their high rate of linear energy transfer over short path lengths. Radium-223 has excellent decay properties but, a major hurdle for its use is the development of a stable chelator for delivery to the tumor site. Work is underway testing polyoxopalladates, as a novel subclass of polyoxometalates (POMs), to complex barium and radium and establish the feasibility of their radiopharmaceutical use. Nonradioactive BaPd15 POMs were produced by the reported literature method and characterized by NMR, TLC, and HPLC. Radioactive [133Ba, 224Ra]BaPd15 POMs were prepared similarly with either [133Ba]BaCl2 or [224Ra]RaCl2 spiked into the solution prior to heating. Characterization was performed by NMR, RadioTLC, and HPLC. Chromatographic separations were tested using Dowex-50 and Sephadex G-15 to purify the POM product. Dialysis studies were carried out to determine the stability of the [133Ba]BaPd15. Incubation studies with rat serum were performed to explore their biological stability. The POMs were easily prepared in a one-pot reaction and characterized by 1H and 13C NMR. TLC and HPLC were performed to determine the percent of incorporated radionuclide. Cation exchange chromatography with Dowex 50-X8 removed free [133Ba]Ba2+ to non-detectable levels in the product. Size exclusion chromatography with Sephadex G-15 separated the BaPd15 product (eluted first) from the bulk excess of acetate buffer and phenylarsonic acid. Dialysis studies showed measurable quantities of 133Ba in solution after 1 hour and ~ 10% of the radionuclide had escaped after 24 hours. Serum studies indicated the POMs had affinity for serum proteins quickly upon contact with the serum. The results of this study demonstrate the development of radioactive [133Ba, 224Ra]BaPd15 POMs. Stability studies indicated that these POMs quickly began to decompose, significantly so after 24 hours. Additionally, incubation studies with rat serum demonstrated an affinity for serum proteins. For these reasons, these POMs are unsuitable for radiotherapeutic use.
Keywords: Polyoxometalates, Alpha-therapy, Radium
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), Dresden, 14.-19.05.2017, Dresden, Deutschland
  • Open Access Logo Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, S559
    DOI: 10.1002/jlcr.3508

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Permalink: https://www.hzdr.de/publications/Publ-26076
Publ.-Id: 26076


Synthesis of a Cu-Filled Rh17S15 Framework: Microwave Polyol Process Versus High-Temperature Route

Roslova, M.; Golub, P.; Opherden, L.; Ovchinnikov, A.; Uhlarz, M.; Baranov, A. I.; Prots, Y.; Isaeva, A.; Coduri, M.; Herrmannsdörfer, T.; Wosnitza, J.; Doert, T.; Ruck, M.
Metal-rich, mixed copper−rhodium sulfide Cu3−δRh34S30 that represents a new Cu-filled variant of the Rh17S15 structure has been synthesized and structurally characterized. Copper content in the [CuRh8] cubic cluster was found to vary notably dependent on the chosen synthetic route. Full site occupancy was achieved only in nanoscaled Cu3Rh34S30 obtained by a rapid, microwave-assisted reaction of CuCl, Rh2(CH3CO2)4 and thiosemicarbazide at 300 °C in just 30 min; whereas merely Cu-deficient Cu3−δRh34S30 (2.0 ≥ δ ≥ 0.9) compositions were realized via conventional high-temperature ceramic synthesis from the elements at 950 °C. Although Cu3−δRh34S30 is metallic just like Rh17S15, the slightly enhanced metal content has a dramatic effect on the electronic properties. Whereas the Rh17S15 host undergoes a superconducting transition at 5.4 K, no signs of the latter were found for the Cu-derivatives at least down to 1.8 K. This finding is corroborated by the strongly reduced density of states at the Fermi level of the ternary sulfide and the disruption of long-range Rh−Rh interactions in favor of Cu−Rh interactions as revealed by quantum-chemical calculations.

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Permalink: https://www.hzdr.de/publications/Publ-26075
Publ.-Id: 26075


Novel Functionalized Calixarenes as Host Molecules for Complexation with Alkaline Earth Metals

Steinberg, J.; Gott, M.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.
Alpha-emitting radionuclides (e.g. radium-223, 224) are of high interest for cancer therapy, but currently, no stable complexing agent for radium is known. Moderate stability constants have been described for complexes of alkaline-earth metal ions with calixarenes, crown and aza crown ethers [2, 3]. By combining calixarenes with crown and aza crown ethers as well as functionalizing the remaining calixarene hydroxyl groups, higher stability constants may be achieved. In this study, we synthesized and evaluated new functionalized calixarenes as host molecules for radium. 1,3 single-bridged crowns were selectively introduced on the lower rim of 4-tert-Butylcalix[4]arene by alkylation with tosylated crown ethers or by acylation and sequential amination with aza crown ethers. The remaining phenolic hydroxyl groups were functionalized by acylation and sequential amination to prepare acetic acid amide and hydroxyl amide derivatives. The complexation was carried out by vortexing the ligand in chloroform with an aqueous BaCl2-solution as surrogate for Ra for 10 min. The barium complex was isolated from the organic layer and characterization was performed by NMR. The barium-133 and radium-224 calixcrowns were prepared similarly and stability studies performed by TLC and HPLC. 1,3-bridged crown and calix(aza)crown ethers were obtained in good yields (53 and 58%, respectively) and acetic acid amide and hydroxyl amide calixcrown derivatives were successfully prepared with yields of 66-82%. Barium was incorporated into the calixarene compounds, isolated by a two-phase extraction and the structure confirmed by NMR. Synthesis and stability of the radioactive complexes will be reported. Future studies will incorporate a targeting moiety on the upper ring. Several novel, functionalized calixarene compounds were prepared and initial complexation studies were performed with nonradioactive barium. The resulting complexes were checked by NMR and the procedure was transferred to radioactive barium-133 and radium-224. Complexation and stability was demonstrated by radiographic imaging of the developed TLC plates. These complexes show great promise for application to cancer therapy.
Keywords: Alpha-therapy, Radium, Calixarenes
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), Dresden, 14.-19.05.2017, Dresden, Deutschland
  • Open Access Logo Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, S488
    DOI: 10.1002/jlcr.3508

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Permalink: https://www.hzdr.de/publications/Publ-26074
Publ.-Id: 26074


Combining in situ synchrotron X-ray diffraction and X-ray radiography to study the dendritic growth in Ga–In alloys

Shevchenko, N.; Grenzer, J.; Keplinger, O.; Rack, A.; Cantelli, V.; Eckert, S.
Dendrites are common microstructures that are formed during industrial casting or welding. The processes involved in the formation of different dendrite morphologies and the orientation selection during dendritic growth are rather complex and still far from being fully understood [1-3]. In this work, in situ synchrotron X-ray radiography and diffraction methods have been combined to study the evolution of dendritic microstructures during the solidification of Ga - In alloys. The in situ directional solidification experiments were performed at the ID19 and BM20 beamlines (ESRF, France) at a high spatial resolution of < 1 µm.
Solidification processes are affected by natural convection as soon as instable density stratification arises in the melt. Melt flow induces various effects on the dendrite and grain morphology primarily caused by the convective transport of the solute. Usually, the morphologies of these dendrites differ from those developing under purely diffusive condition. Our observations show a facilitation of the growth of primary trunks or lateral branches, a suppression of side branching, dendrite remelting and fragmentation [4]. The final microstructure reveals dendrites with random and complicated morphologies.
The flow-induced variations of the local solute concentration may result in the changes of dendrite crystal orientations. According to theoretical predictions, the dendrite growth directions should not follow necessarily low indexed crystallographic directions [1]. Therefore coupling of in situ X-ray imaging with X-ray diffraction provides additionally information of the crystallographic orientation of the growing dendrites. Our measurements show that majority of the Indium dendrites grow along the <110> orientation, typically observed in body-centered metals. The analysis of the diffraction patterns obtained from the complex dendritic structures shows that a further improvement towards a 3D imaging experiment is needed. These first results demonstrate that the combination of these X-ray techniques can provide new data about the solidification processes and help to validate microstructural solidification models.
This work is financially supported by the Helmholtz Association “LIMTECH”.
Keywords: Dendrites, solidification, in situ synchrotron radiography, X-ray diffraction
  • Poster
    ESRF User Meeting, 06.-08.02.2017, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-26073
Publ.-Id: 26073


Detection of Auger Electron Induced Strand Breaks on Plasmid DNA Caused by Technetium-99m Labeled Pyrene Derivatives

Wunderlich, G.; Reissig, F.; Mamat, C.; Pietzsch, H.-J.; Kotzerke, J.; Steinbach, J.
Simultaneously with the known γ-emission, 99mTc causes radical-mediated DNA damage due to Auger electrons, which were also emitted. We have synthesized a series of new 99mTc-labeled pyrene derivatives (common DNA intercalators) with varied distances between the pyrene moiety and the radionuclide (Fig. 1). Plasmids (pUC 19) enable the investigation of the unprotected interactions between the labeled pyrene derivatives (3-15MBq) and DNA that results in single-strand breaks (SSB) or double-strand breaks (DSB) separated by gel electrophoresis in 1.4% agarose gel and quantified by fluorescent staining. We used the 99mTc(CO)3-core for pyrene labeling. 99mTc was tightly bound to the plasmid DNA and its damage is mainly dependent on the chain length between the pyrene residue and the Tc-core. It could not be completely prevented by DMSO, a known free radical scavenger. The effectiveness of the DNA-binding 99mTc-labeled pyrene derivatives was demonstrated by comparison to non-DNA-binding [99mTc]NaTcO4, since nearly all DNA damage caused by [99mTc]NaTcO4 was prevented by DMSO. We prepared a 99mTc-complex with an optimal distance between the [99mTc]Tc(CO)3-core and the pyrene residue to position the 99mTc in close proximity to the plasmid DNA to induce direct SSB and DSB. By increasing the distance between the DNA-intercalating moiety and the bonding moiety for 99mTc, we observed decrease of direct DNA damages. This distance dependence has not been reported for 99mTc until now. Clinical relevant Auger electron therapy is hampered by the prerequisite of DNA binding which is hindered by cell and nucleus membranes.
Keywords: 99mTc, Auger, DNA damage, Therapy
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), Dresden, 14.-19.05.2017, Dresden, Deutschland
  • Open Access Logo Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, S365
    DOI: 10.1002/jlcr.3508

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Permalink: https://www.hzdr.de/publications/Publ-26072
Publ.-Id: 26072


Evaluation of Safety of Light Water Cooled Reactors using CFD

Höhne, T.
Computational Fluid Dynamics (CFD) is increasingly being used in nuclear reactor safety (NRS) analyses as a tool that enables safety relevant phenomena occurring in the reactor coolant system to be described in more detail.

Numerical investigations on single phase coolant mixing in Pressurized Water Reactors (PWR) have been performed at the FZD for almost a decade. The work is aimed at describing the mixing phenomena relevant for both safety analysis, particularly in steam line break and boron dilution scenarios, and mixing phenomena of interest for economical operation and the structural integrity.

On the other hand slug flow as a multiphase flow regime can occur in the cold legs of pressurized water reactors, for instance after a small break Loss of Coolant Accident (SB-LOCA). Slug flow is potentially hazardous to the structure of the system due to the strong oscillating pressure levels formed behind the liquid slugs. For the experimental investigation of horizontal two phase flows, different non pressurized channels and the TOPFLOW Hot Leg model in a pressure chamber was build and simulated with ANSYS CFX.
Keywords: NRS, LOCA, TOPFLOW, AIAD, CFX, CFD
  • Book chapter
    Arun Nayak: Advances of Computational Fluid Dynamics in Nuclear Reactor Design and Safety Assessment, Amsterdam: Elsevier, 2019, 9780081023372, 337-386
    DOI: 10.1016/B978-0-08-102337-2.00004-3

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Permalink: https://www.hzdr.de/publications/Publ-26071
Publ.-Id: 26071


Stratified and Segregated Flow Modelling - AIAD 2017

Höhne, T.
Today: Limits in simulating stratified & segregated two phase flow
Algebraic Interfacial Area Density Model (AIAD)
Free Surface Drag
Turbulence Damping
Sub-grid wave turbulence (SWT)
Verification and Validation is going on – more experimental data are required for the validation
Keywords: AIAD, Free Surface Drag, Sub-grid wave turbulence (SWT)
  • Lecture (Conference)
    15th Short Course “Multiphase Flow: Simulation,Experiment and Application”, 14.-17.11.2017, Dresden, Deutschland
  • Contribution to proceedings
    15th Short Course “Multiphase Flow: Simulation,Experiment and Application”, 14.-17.11.2017, Dresden, Deutschland
  • Poster
    15th Short Course “Multiphase Flow: Simulation,Experiment and Application”, 14.-17.11.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26070
Publ.-Id: 26070


Dipole strength in 80Se below the neutron-separation energy for the nuclear transmutation of 79Se

Makinaga, A.; Massarczyk, R.; Beard, M.; Schwengner, R.; Otsu, H.; Müller, S.; Röder, M.; Schmidt, K.; Wagner, A.
The gamma-ray strength function ( SF) in 80Se is an important parameter to estimate the neutron-capture cross section of 79Se which is one of the long-lived fission products (LLFPs). Until now, the SF method was applied for 80 Se only above the neutron-separation energy (Sn) and the evaluated 79 Se(n,gamma) cross section has an instability caused by the GSF below Sn . We studied the dipole-strength distribution of 80 Se in a photon-scattering experiment using bremsstrahlung produced by an electron beam of an energy of 11.5 MeV at the linear accelerator ELBE at HZDR. The present photoabsorption cross section of 80 Se was combined with results of (gamma,n) experiments and are compared with predictions usinmg the TALYS code. We also estimated the 79 Se(n,gamma) cross sections and compare them with TALYS predictions and earlier work by other groups.
Keywords: Photon scatterinmg, photoabsorption, cross sections, dipole strength, neutron capture, statistical reaction models.

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Permalink: https://www.hzdr.de/publications/Publ-26069
Publ.-Id: 26069


Pharmacokinetic/ pharmacodynamic studies of a copper-64 labelled Kv1.3-blocking peptide targeting autoimmune diseases

Kubeil, M.ORC; Bergmann, R.; Zarschler, K.; Stephan, H.; Norton, R. S.
Objectives
The voltage-gated potassium channel Kv1.3 is an attractive therapeutic target to treat autoimmune disorders such as multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus and type-1 diabetes mellitus [1, 2]. This channel is highly expressed in T
effector memory lymphocytes and plays an important role in their activation. A scorpion toxin derived peptide analogue, HsTX1[R14A], blocks Kv1.3 with an affinity in the picomolar range [3].Moreover, this peptide is stabilized by four disulfide bridges, conferring high in vivo stability.
Methods
The peptide was synthesised by SPPS using Fmoc-tBu strategy [3]. The N-terminus of HsTX1[R14A] has been coupled to NOTA (1,4,7-triazacyclononane-triacetic acid) to permit labelling with the positron emitter copper-64. Biodistribution studies and metabolite analysis were carried out in healthy male Wistar rats using Positron Emission Tomography and Radioluminography.
Results
The distribution studies demonstrated a rapid blood clearance after intravenous injection and a fast renal elimination. The highest accumulation was found in the kidney and urine. As a consequence, a long in vivo half-life has been observed. Furthermore, there were no indications of lymphatic cell binding in direct measurements with unfractionated human Tcells.
Conclusion
The promising pharmacological profile of the radiotracer enhances the potential of this peptide to be developed as a therapeutic. Its extraordinary stability and high selectivity for the target channel Kv1.3 make it an attractive candidate for autoimmune disorders.
References
[1] V. Chi, M. W. Pennington, R. S. Norton, E. Tarcha, L. Londono, B. Sims-Fahey, S. K. Upadhyay, J. T. Lakey, S. Iadonato, H. Wulff, C. Beeton, K. G. Chandy, Toxicon 2012, 59, 529-546.
[2] C. Beeton, et al. Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 17414-17419.
[3] M. H. Rashid, R. Huq, M. R. Tanner, S. Chhabra, K. K. Khoo, R. Estrada, V. Dhawan, S. Chauhan, M. W. Pennington, C. Beeton, S. Kuyucak, and R. S. Norton, Sci. Rep. 2014, 4, 1-9.
Keywords: potassium channel, autoimmune disease, PET, peptide
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences, 14.-19.05.2017, Dresden, Deutschland

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Publ.-Id: 26068


Neuartige Calix[4]arene zur Komplexierung von Erdalkalimetallen

Mamat, C.ORC; Bauer, D.; Gott, M.; Pietzsch, H.-J.; Steinbach, J.; Steinberg, J.
Radium-223 und Radium-224 sind klassische alpha-Emitter, die u.a. zu radiotherapeutischen Zwecken Verwendung finden sollen. Radium-223 ist bereits in der klinischen Anwendung, jedoch lediglich als [223Ra]RaCl2, da geeignete Chelatoren für eine stabile Komplexierung dieses Gruppe-2-Metalls fehlen. Komplexbildner die aus (Aza-)Kronenethern und Calixarenen bestehen stellen vielversprechende Kandidaten dar. Von dieses Derivaten wurden Komplexbildungskonstanten bestimmt mit Ba2+ als nichtradioaktives Surrogat aufgrund der ähnlichen chemischen Eigenschaften. Des Weiteren wurden Komplexierungsstudien mit 133Ba durchgeführt.
Keywords: Calixarene, Radium-223, Radiotherapeutika, alpha-Emitter
  • Lecture (Conference)
    Wissenschaftsforum Berlin - GdCh-Jahrestagung, 10.-13.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26067
Publ.-Id: 26067


Dipolar interaction induced band gaps and flat modes in surface-modulated magnonic crystals

Gallardo, R. A.; Schneider, T.; Roldan-Molina, A.; Langer, M.; Fassbender, J.ORC; Lenz, K.; Lindner, J.; Landeros, P.
Theoretical results for the magnetization dynamics of surface-modulated magnonic crystals (SMMCs) are presented. For such systems, the role of the periodic dipolar field induced by the geometrical modulation is addressed by using the plane-wave method. The results unveil that under the increasing of the etched depth, zones with magnetizing and demagnetizing fields act on the system, in such a way that magnonic band gaps are observed in both Damon-Eshbach (DE) and backward volume (BV) geometries. Particularly, in BV configuration, high frequency band gaps and low frequency nearly at modes are obtained. By controlling the geometry of the etched zones, the frequency modes, spatial profiles and forbidden frequency gaps of spin waves (SWs) can be manipulated. To test the validity of the model, the theoretical results of this work are confirmed by micromagnetic simulations, where a good agreement between both methods is achieved. It is demonstrated that the spin-wave dynamics of a surface modulated magnonic crystal contrasts to bi-component magnonic crystals or periodic arrays of wires, for instance, since the SMMCs allow enhancing the magnetizing character in some regions of the film, promoting thus the confinement of the SWs. The theoretical model allows for a detailed understanding of the physics underlying these kind of systems, thereby providing an outlook to potential applications on magnonic devices.
Keywords: magnonic crystals, spin waves, ferromagnetic resonance, magnetization dynamics

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New measurement of the 242Pu(n,γ) cross section at n_TOF-EAR1 for MOX fuels: Preliminary results in the RRR

Lerendegui-Marco, J.; Guerrero, C.; Cortés-Giraldo, M. A.; Quesada, J. M.; Mendoza, E.; Cano-Ott, D.; Eberhardt, K.; Junghans, A.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Bečvář, F.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brown, A.; Caamaño, M.; Calviño, F.; Calviani, M.; Cardella, R.; Casanovas, A.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Göbel, K.; Gómez-Hornillos, M. B.; García, A. R.; Gawlik, A.; Gilardoni, S.; Glodariu, T.; Gonçalves, I. F.; González, E.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Kalamara, A.; Kavrigin, P.; Kimura, A.; Kivel, N.; Kokkoris, M.; Krtička, M.; Kurtulgil, D.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lo Meo, S.; Lonsdale, S. J.; Macina, D.; Marganiec, J.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Maugeri, E. A.; Mazzone, A.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Musumarra, A.; Negret, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, I.; Praena, J.; Radeck, D.; Rauscher, T.; Reifarth, R.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Smith, A. G.; Sosnin, N. V.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Warren, S.; Woods, P. J.; Wright, T.; Žugec, P.; The N_Tof Collaboration
The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with 238U 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. The use of MOX fuels in thermal and fast reactors requires accurate capture and fission cross sections. For the particular case of 242Pu, the previous neutron capture cross section measurements were made in the 70's, providing an uncertainty of about 35% in the keV region. In this context, the Nuclear Energy Agency recommends in its “High Priority Request List” and its report WPEC-26 that the capture cross section of 242Pu should be measured with an accuracy of at least 7–12% in the neutron energy range between 500 eV and 500 keV. This work presents a brief description of the measurement performed at n_TOF-EAR1, the data reduction process and the first ToF capture measurement on this isotope in the last 40 years, providing preliminary individual resonance parameters beyond the current energy limits in the evaluations, as well as a preliminary set of average resonance parameters.
Keywords: 242Pu neutron capture, neutron time-of-flight measurement, CERN nTOF
  • Open Access Logo Contribution to proceedings
    International Conference on Nuclear Data for Science and Technology (ND2016), 11.-16.09.16, Bruges, Belgium, 11.-16.09.16, Bruges, Belgium
    European Physical Journal Web of Conferences
    DOI: 10.1051/epjconf/201714611045

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Positron Annihilation Studies using a Superconducting Electron LINAC

Wagner, A.; Butterling, M.; Hirschmann, E.; Krause-Rehberg, R.; Liedke, M. O.; Potzger, K.
The Helmholtz-Center at Dresden-Rossendorf operates several user beamlines for materials research using positron annihilation energy and lifetime spectroscopy. Two beamlines are being operated at a superconducting electron linear accelerator producing hard X-rays from electron-bremsstrahlung and in turn generating positrons from pair production. Both installations employ bunched continuous-wave (CW) electron beams with energies between 15 MeV and 30 MeV. The CW-operation results in significantly reduced pile-up effects in the detectors in comparison to normal conducting accelerators. Electron bunch lengths below 10 ps FWHM allow positron annihilation lifetime spectroscopy measurements with high timing resolutions. The bunch repetition rate is adjustable to 26 MHz / 2n, n=0, 1, 2 ... 16 matching wide spans in positron or positronium lifetimes. The GiPS (Gamma-induced Positron Source) generates energetic electron-positron pairs inside the sample under investigation from hard x-rays impinging onto the sample [2]. Therefore, the source is especially suited for materials which are not qualified for vacuum conditions or because they are imposing hazardous conditions or intrinsic radioactivity. Exemplary defect studies on the skyrmoin-lattice compound MnSi will be presented. MePS (the Monoenergetic Positron Source) utilizes positrons with fixed energies ranging from 500 eV to 16 keV. A magnetic beam transport system guides positrons to the samples under investigation. A dedicated chopper/buncher system is used to maintain a high timing resolution for depth-dependent annihilation lifetime studies in thin films. The signal-to-noise ratio is beyond 104 while lifetime resolutions of around 280 ps FWHM have been obtained. Applications of porosimetry studies in low-k dielectrics and polymer brushes will be presented.
The MePS facility will be extended by an end-station called AIDA2 (Apparatus for in-situ Defect Analysis) where defect studies can be performed in a wide temperature range during thin film growth and ion irradiation. A similar setup named AIDA-1 is already in operation at a 22Na-based mono-energetic continuous positron beam used for Doppler-broadening spectroscopy experiments.
The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). The initial AIDA system was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox). The AIDA facility was funded through the Helmholtz Energy Materials Characterization Platform.
Keywords: positron annihilation superconducting LINAC materials science
  • Invited lecture (Conferences)
    International Workshop on Physics with Positrons at Jefferson Lab, 12.-15.09.2017, Newport News, VA, USA
  • Invited lecture (Conferences)
    International Workshop on Positron Studies of Defects 2017 (PSD-17), 03.-08.09.2017, Dresden, Deutschland
  • Open Access Logo AIP Conference Proceedings 1970(2018), 040003
    DOI: 10.1063/1.5040215
  • Lecture (Conference)
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 12.-16.03.2018, Berlin, Deutschland

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Liquid metal batteries

Weier, T.; Ashour, R.; Herreman, W.; Horstmann, G.; Kelley, D.; Landgraf, S.; Nimtz, M.; Nore, C.; Personnettaz, P.; Salas, A.; Starace, M.; Stefani, F.; Weber, N.
Übersicht der Forschungsaktivitäten zu Flüssigmetallbatterien am HZDR
  • Poster
    LIMTECH-Symposium, 19.09.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26063
Publ.-Id: 26063


Chemical and Electronic Repair Mechanism of Defects in MoS2 Monolayers

Förster, A.; Gemming, S.; Seifert, G.; Tománek, D.
Using ab initio density functional theory cal- culations, we characterize changes in the elec- tronic structure of MoS2 monolayers introduced by missing or additional adsorbed sulfur atoms. We furthermore identify the chemical and elec- tronic function of substances that have been reported to reduce the adverse effect of sul- fur vacancies in quenching photoluminescence and reducing electronic conductance. We find that thiol-group containing molecules adsorbed at vacancy sites may re-insert missing sulfur atoms. And in the presence of sulfur adatoms, thiols may form disulfides on the MoS2 surface to mitigate the adverse effect of defects.
Keywords: 2D materials, TMD, defects, density-functional, transition metal dichalcogenide, nanoelectronics, catalysis

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Publ.-Id: 26062


High repetition rate, multi-MeV proton source from cryogenic hydrogen jets

Gauthier, M.; Curry, C. B.; Göde, S.; Brack, F.-E.; Kim, J. B.; Macdonald, M. J.; Metzkes, J.; Obst, L.; Rehwald, M.; Rödel, C.; Schlenvoigt, H.-P.; Schumaker, W.; Schramm, U.; Zeil, K.; Glenzer, S. H.
We report on a high repetition rate proton source produced by high-intensity laser irradiation of a continuously flowing, cryogenic hydrogen jet. The proton energy spectra are recorded at 1Hz for Draco laser powers of 6, 20, 40, and 100 TW. The source delivers ca. 10^13 protons/MeV/sr/min. We find that the average proton number over one minute, at energies sufficiently far from the cut-off energy, is robust to laser-target overlap and nearly constant. This work is therefore a first step towards pulsed laser-driven proton sources for time-resolved radiation damage studies and applications which require quasi-continuous doses at MeV energies.

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Publ.-Id: 26061


Nitrogen redistribution in annealed LaFeOxNy thin films investigated by FTIR spectroscopy and EELS mapping

Haye, E.; Pierron, V.; Barrat, S.; Capon, F.; Munnik, F.; Bruyère, S.
LaFeOxNy thin films have been deposited by magnetron sputtering in Ar/O2/N2 gas mixture at 800°C. Such oxynitride perovskites present an uncommon infrared vibration mode position at 2040cm-1, due to presence of nitrogen, which disappears with heating in air. The evolution of this vibration mode with temperature has been studied and permit to determine an activation energy of thermal degradation of LaFeOxNy. The quantification of nitrogen by Elastic Recoil Detection Analysis (ERDA) before and after heating exhibits the same nitrogen content, indicating a redistribution of nitrogen. Such nitrogen redistribution is observed by Electron Energy Loss Spectroscopy (EELS) mapping, showing migration of nitrogen into grain boundaries, in association with film oxidation.
Keywords: Oxynitride perovskite, Thermal stability, EELS mapping, FTIR

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