Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34800 Publications

Dose Controlled Radiobiological Experiments with Ultra-short Pulse Laser Accelerated Proton Pulses

Schramm, U.; Beyreuther, E.; Cowan, T.; Metzkes, J.; Sauerbrey, R.; Zeil, K.; Kraft, S.; Richter, C.; Enghardt, W.; Karsch, L.; Pawelke, J.

Over the last decade laser particle acceleration has made such progress that first applications in special fields can be envisioned. Prominent examples are radiation therapy with laser accelerated ion beams as well as the generation of pulsed X-ray sources. Here the demonstration of laser acceleration of proton pulses to maximum energies in the range of up to 20 MeV making use of the 100 TW table-top laser Draco installed at HZDR Dresden will be reported. Reproducible conditions over thousands of shots allowed for the first dose controlled irradiation of in vitro tumor cell samples, representing the first step towards radiobiological applications. A detailed description of experimental requirements as sufficiently high proton energies providing applicable doses of a few Gy within minutes, a beam transport and filtering system, an in-air irradiation site, a dedicated dosimetry system providing both online dose monitoring and a precise absolute dose information applied to the cell sample will be given.

Keywords: Laser ion acceleration; cancer therapy

  • Poster
    IPAC 2012, 21.-25.05.2012, New Orleans, LA, USA

Permalink: https://www.hzdr.de/publications/Publ-17203
Publ.-Id: 17203


Picosecond Narrow Bandwidth X-ray Pulses from a Laser-Thomson-Backscattering Source

Jochmann, A.; Cowan, T.; Kuntzsch, M.; Lehnert, U.; Sauerbrey, R.; Wagner, A.; Trotsenko, S.; Couperus, J. P.; Debus, A.; Irman, A.; Schlenvoigt, H.-P.; Schramm, U.; Ledingham, K.

Intense, ultimately coherent, ultrashort hard X-ray pulses can serve as a novel tool for structural analysis of complex systems with unprecedented temporal and spatial resolution. With the simultaneous availability of a high power short-pulse laser system it provides unique opportunities for a number of subsequent research steps at the forefront of relativistic light-matter interactions. At HZDR we demonstrated the generation of such a light source (PHOENIX) by colliding picosecond electron bunches from the ELBE linear accelerator with counter-propagating femtosecond laser pulses from the 150 TW Draco Ti:Sapphire laser system. The generated narrowband X-rays are highly collimated and can be reliable adjusted from 5.5 to 23.5 keV by tuning the electron energy (24 MeV to 30 MeV) and the laser intensity. Ensuring the spatiotemporal overlap and suppressing the bremsstrahlung background we have achieved a signal-to-noise ratio greater than 300:1. Together with the use of an X-ray camera (resolution of 250 eV(FWHM)) to record the spectrum, we were able to resolve the angular-energy correlation and to study the influence of the beam emittance on the observed bandwidth.

Keywords: X-ray light sources; Thomson scattering

  • Poster
    IPAC 2012, 21.-25.05.2012, New Orleans, LA, USA

Permalink: https://www.hzdr.de/publications/Publ-17202
Publ.-Id: 17202


Extension and application of the reactor dynamics code DYN3D for Block-type High Temperature Reactors

Baier, S.; Fridman, E.; Kliem, S.; Rohde, U.

The reactor dynamics code DYN3D was developed at the Helmholtz-Zentrum Dresden-Rossendorf to study steady state and transient behavior of Light Water Reactors. Concerning the neutronics part, the multigroup diffusion or SP3 transport equation based on nodal expansion methods is solved both for hexagonal and square fuel element geometry. To deal with Block-type High Temperature Reactor cores DYN3D was extended to a version DYN3D-HTR. A 3D heat conduction model was introduced to include 3D effects of heat transfer and heat conduction and the detailed structure of the fuel element. Results of coupled steady state and transient calculations with 12 energy groups are presented. Transient case studies are control rod insertion a change of the inlet coolant temperature and a change of the coolant gas mass flow rate. It is shown that DYN3D-HTR is an appropriate code system to simulate steady states and short time transients. Furthermore the necessity of the 3D heat conduction model is demonstrated.

Keywords: high temperature gas cooled reactor; heat conduction model; transient analysis; computer code; temperature reactivity feedback

  • Contribution to proceedings
    6th International Topical Meeting on High Temperature Reactor Technology HTR2012, 28.10.-01.11.2012, Tokyo, Japan
  • Nuclear Engineering and Design 271(2014), 431-436
    DOI: 10.1016/j.nucengdes.2013.12.013

Permalink: https://www.hzdr.de/publications/Publ-17201
Publ.-Id: 17201


Precise millisecond annealing for advanced material processing

Reichel, D.; Skorupa, W.

Flash Lamp Annealing (FLA) reduces the thermal budget on the bulk and thus hinders undesired thermal diffusion. For reliable process control, however, a temperature measurement concept is needed that is capable of facing the high radiation background of the flash lamps and the millisecond detection regime at the same time [1]. A new concept has been developed for precise in-situ temperature measurement during flash-lamp Millisecond Annealing. There has been taking advantage of FLA for various applications. Implantation and subsequent FLA were used to obtain III-V semiconductor quantum dots on silicon pillars [2]. The same procedure was applied to achieve superconductivity with conventional silicon technolog [3]. FLA was further used for advanced doping of “dirty-silicon” solar cells. The short annealing cycles allow for successful dopant activation while undesired metal impurities remain electrically inactive [4]. These examples show that in-situ process control is required to make sure the major advantage of Millisecond Annealing is not narrowed by unreliable temperature measurement. In this contribution, a method will be presented that satisfies this issue by in-situ distinction between thermal and flash lamp radiation.

Keywords: annealing; millisecond; flash lamps; temperature measurement

  • Contribution to proceedings
    EMRS Spring Meeting 2012, 14.-18.05.2012, Strasbourg, France
    Advanced Silicon Materials Research for Electronic and Photovoltaic Applications III
  • Poster
    EMRS Spring Meeting 2012, 14.-18.05.2012, Strasbourg, France
  • Physica Status Solidi (C) 9(2012)10-11, 2045-2049
    DOI: 10.1002/pssc.201200277

Permalink: https://www.hzdr.de/publications/Publ-17200
Publ.-Id: 17200


The Factor Cloud Computing in IT Risk Management

Penzina, V. J.; Konrad, U.; Yusupova, N. I.

Der Artikel beschreibt eine Definition und den Prozess des IT Risiko-Managements mit dem besonderen Einfluss von Cloud-Computing, insbesondere die Identifikation von Schwachstellen, Steuermöglichkeiten und Maßnahmen.
Today Risk Management plays a crucial role in protecting information. Effective Risk Management is one of the most important parts of a security program in IT organizations.
This paper represents a definition of Risk Management, first steps of the process and the influence of cloud computing according to vulnerability identification and controls and measures analysis subprocesses.

  • Contribution to proceedings
    The 14th International Workshop on Computer Science and Information Technologies, CSIT’2012, 20.-26.09.2012, MSC Lirica, Norway
    Proceedings of the 14th International workshop on computer science and information technologies, CSIT’2012, Ufa – Hamburg – Norwegian Fjords, 2012

Permalink: https://www.hzdr.de/publications/Publ-17199
Publ.-Id: 17199


Development and implementation of a 3D heat conduction model for (very) High Temperature Reactors into the reactor dynamics code DYN3D

Baier, S.; Rohde, U.; Kliem, S.; Fridman, E.

The reactor dynamics code DYN3D was extended to treat phenomena in Block-type High Temperature Reactors (HTR). Therefor, a new heat conduction model was implemented into the code to tackle 3D effects of heat conduction and heat transfer. The first part of the paper describes the details of the heat conduction model. In the second part results of coupled neutron-kinetics/thermal-hydraulics calculations of steady state and short-time transients in block-type HTRs are discussed.

Keywords: high temperature gas cooled reactor; heat conduction model; transient analysis; computer code; temperature reactivity feedback

  • Contribution to proceedings
    20th International conference on Nuclear Engineering - ICONE20, 30.07.-03.08.2012, Anaheim, USA
    Proceedings of ICONE20
  • Lecture (Conference)
    20th International conference on Nuclear Engineering - ICONE20, 30.07.-03.08.2012, Anaheim, USA

Permalink: https://www.hzdr.de/publications/Publ-17198
Publ.-Id: 17198


Investigation on the structural and magnetic properties of Co+ implanted rutile TiO2

Cheng, F.; Ding, B.; Pan, F.; Yao, S.; Potzger, K.; Zhou, S.

Crystalline Co nanoparticles in rutile TiO2 were synthesized by 180 keV Co+ ion implantation at 623 K with the fluence of Φ = 4 × 1016 cm−2. The structural and magnetic properties of samples after thermal annealing at different temperatures were characterized by synchrotron radiation X-ray diffraction (SR-XRD), Rutherford backscattering/channeling (RBS/C) and superconducting quantum interference device (SQUID) magnetometer. The SR-XRD results reveal the formation of hcp Co nanoparticles in the as-implanted samples. With increasing annealing temperature, the transition of Co nanoparticles from hcp to fcc is observed. After annealing at 1073 K, the lattice damage is significantly repaired compared with the as-implanted one. The Co nanoparticles forming inside TiO2 are the major contribution of the measured ferromagnetism.

Keywords: Rutherford backscattering and channeling; X-ray diffraction; SQUID magnetometers; Magnetic nanoparticles; Ion implantation

Permalink: https://www.hzdr.de/publications/Publ-17197
Publ.-Id: 17197


CFD analysis on the NUPEC PWR Subchannel and Bundle Test (PSBT) - model calibration and influence of turbulence modelling

Krepper, E.; Rzehak, R.

The presentation shows CFD calculations of the void distribution tests of the PSBT benchmark using ANSYS CFX-12.1. First, relevant aspects of the implemented wall boiling model are reviewed highlighting the uncertainties in several model parameters. It is then shown that the measured cross sectionally averaged values can be reproduced well with a single set of calibrated model parameters for different tests cases. For the reproduction of patterns of void distribution cross sections attention has to be focussed on the modelling of turbulence in the narrow channel. Only a turbulence model with the capability to resolve turbulent secondary flows is able to reproduce at least qualitatively the observed void distribution patterns. Furthermore the influence of bubble forces on the void distribution cross sections was shown.

Keywords: CFD; wall boiling; CFX; PSBT benchmark; rod bundle; two phase flow; turbulence; bubble forces

  • Lecture (Conference)
    AER WG C and D Meeting, 31.05.-01.06.2012, Paks, Ungarn

Permalink: https://www.hzdr.de/publications/Publ-17196
Publ.-Id: 17196


Numerical calculations for steam-water CCFL tests using the 1/3rd scale rectangular channel simulating a PWR hot leg

Kinoshita, I.; Murase, M.; Utanohara, Y.; Lucas, D.; Vallée, C.; Tomiyama, A.

In reflux condensation, steam generated in the reactor core and water condensed in a steam generator (SG) form countercurrent flow in a hot leg, which consists of a horizontal pipe, an elbow and an inclined pipe. Both countercurrent air–water and steam–water tests were previously carried out at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) using the 1/3 scale rectangular channel simulating a PWR hot leg installed in the pressure chamber of the TOPFLOW facility. In this paper, in order to evaluate the effects of fluid properties, the steam–water CCFL (countercurrent flow limitation) tests at HZDR were simulated using the CFD software, FLUENT 6.3.26. The computational domain included the reactor vessel simulator, hot leg and SG inlet chamber in order to avoid uncertainties of boundary conditions at both ends of the hot leg. The VOF (volume of fluid) method and two-fluid (2F) model were used. In the 2F model, the combination of three correlations on the interfacial friction coefficients, which had been validated for the 1/15 and 1/5 scale tests at Kobe University, was used as a function of local void fractions. The CCFL characteristics predicted by the 2F and VOF agreed relatively well with the steam–water CCFL data at HZDR but overestimated the effects of fluid properties on CCFL. The VOF simulations were better able to reproduce the fluid properties than the 2F simulations.

Keywords: CCFL; PWR; hot leg; simulation; experiment

Permalink: https://www.hzdr.de/publications/Publ-17195
Publ.-Id: 17195


Nanoscale TiO2 particles: relationship between surface properties and toxicity measurements

Hurel, C.; Clement, L.; Jordan, N.; Weiß, S.; Marmier, N.

Titanium oxides nanoparticles have been widely used in industrial applications such as cosmetics, food industries, environment, paints and surface coatings…Face to their growing use in various domains and the difficulties to separate them from the aqueous phase during wastewaters treatment due to their nanometric size, one can expect that the final host for these particles should be environmental compartments (soil, air and water).
Nanometric-sized particles are known to cause pulmonary damages and to be toxic for mammals (mice, rats). Nevertheless, few studies dealt with the toxic impact of nanoparticles with ecosystems. Previous studies have shown that the toxic effect was dependent (i) on the size of the particles and (ii) on the allotropic form of TiO2 (anatase or rutile). But a lack of information remains concerning the relationship between the surface properties of TiO2 nanoparticles (surface site density, surface charge) and the observed toxicity.
In this study we were interested in anatase (15 nm, 32 nm, 44 μm) and rutile (1 μm) commercial particles. Their toxic effect (acute or chronic) versus microcrustaceans, algae and plants was measured and compared to the particles size. Surface properties of each TiO2 particles were determined by acid-base titration, and electrokinetics measurements, in order to complete data concerning the relationship between nanoparticles toxicity, size and allotropic form.

Keywords: TiO2; nanoparticles; toxicity

  • Lecture (Conference)
    Interfaces Against Pollution, 11.-14.06.2012, Nancy, France

Permalink: https://www.hzdr.de/publications/Publ-17194
Publ.-Id: 17194


Focused Ion Beams - Status and New Trends

Bischoff, L.

In the last decade focused ion beams (FIB) became an irrecoverable instrument in research and industry. Sample preparation, local ion implantation and ion analysis are the main application topics. Most of the systems are equipped with a gallium liquid metal ion source (LMIS). But, modern trends in nanotechnology require more extended properties like variable ion species, non-contaminating milling at higher rates or higher lateral resolution in the field of ion microscopy [1].
In this presentation the implementation of an alloy LMIS in a mass separated FIB system is introduced. Fabrication and characterization of such sources will be briefly shown and prospective applications like self-organized surface modification with focused heavy cluster ions on a germanium surface or local ion beam syntheses of CoSi2 nanostructures are demonstrated.
Furthermore the status and application of new source concepts including prototypes will be reviewed in particular high current gas sources (ECR, ICP) for effective high rate milling, ion trap sources providing highly charged ions or used for SIMS applications as well as gas field ion sources for high resolution ion microscopy in the sub-nm range. Additionally, the use of alloy liquid metal ion sources and its characterization for mass separated FIB systems and ToF-SIMS applications will be presented. New trends and possibilities in FIB employment will be discussed.

Keywords: FIB; LMIS; Mass sparation; alternative FIB Sources; SIMS

  • Invited lecture (Conferences)
    ITG WORKSHOP: Vacuum Electronics 2012, 20.-21.08.2012, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-17193
Publ.-Id: 17193


Modern Trends in FIB Development

Bischoff, L.

In the last decade focused ion beams (FIB) became an irrecoverable instrument in research and industry. Sample preparation, local ion implantation and ion analysis are the main application topics. Most of the systems are equipped with a gallium liquid metal ion source (LMIS). But, modern trends in nanotechnology require more extended properties like variable ion species, non-contaminating milling at higher rates or higher lateral resolution in the field of ion microscopy.
In this presentation the application of alloy LMIS in a mass separated FIB system is introduced as well as new source concepts will be reviewed including high current gas sources for effective milling, ion trap sources for highly charged ions or SIMS applications and high resolution gas field ion sources for ion microscopy in the sub-nm range.
New trends and possibilities in FIB employment will be discussed.

Keywords: focused ion beams; liquid metal ion source; mass separated FIB system; new source concepts

  • Invited lecture (Conferences)
    7. FIB-Workshop Focused Ion Beams in Research, Science and Technology, 25.-27.06.2012, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-17192
Publ.-Id: 17192


Cyclotron resonance spectroscopy

Drachenko, O.; Helm, M.

We give an overview of the basic theory of cyclotron resonance, discuss some experimental aspects of cyclotron resonance spectroscopy in high, mostly pulsed magnetic fields, and finally discuss some recent cyclotron resonance experiments on various semiconductor materials.

Keywords: cyclotron resonance; high magnetic field; infrared

  • Book chapter
    Amalia Patane, Naci Balkan: Semiconductor Research, Berlin-Heidelberg: Springer-Verlag, 2012, 978-3-642-23350-0, 283-307

Permalink: https://www.hzdr.de/publications/Publ-17191
Publ.-Id: 17191


German SFR research and european sodium fast reactor project

Merk, B.

In the first part an overview on the fast reactor related work at HZDR is given with the focus on liquid metal technology for sodium cooled fast reactors, on a method to created enhanced feedback effects in sodium cooled fast reactors, and on the development of DYN3D for fast reactor applications. A short insight into the german contributions to the IAEA EBR-II benchmark and on the SFR work at KIT is presented. The second part consists of an overview on the safety related work packages of the 7. Framework Program project ESFR.

Keywords: enhanced feedback effects; liquid metal technologies; DYN3D for fast reactors; ESFR

  • Invited lecture (Conferences)
    International Workshop on Prevention and Mitigation of Severe Accidents in Sodium-cooled Fast Reactors, 12.-13.06.2012, Tsuruga, Japan

Permalink: https://www.hzdr.de/publications/Publ-17190
Publ.-Id: 17190


First Experience at ELBE with the new 1.3 GHz CW RF-System based on 10kW Solid State Amplifiers

Büttig, H.; Arnold, A.; Büchner, A.; Justus, M.; Kuntzsch, M.; Lehnert, U.; Michel, P.; Schurig, R.; Staats, G.; Teichert, J.

With the expansion of the radiation source ELBE, a centre for high power radiation sources is being built between 2009 and 2014 at the Helmholtz Zentrum Dresden Rossendorf. One part of this program is to increase the beam current of the ELBE LINAC. In January 2012 each of the 10kW CW klystrons used to operate the superconducting cavities of ELBE since 2001 had been replaced by a pair of 10kW solid state amplifiers.The talk gives an overview on the new RF-system of ELBE and its performance.

Keywords: ELBE RF; Solid State Power Amplifier 10 kW 1300MHz; 10kW SSPA 1300MHz; Superconducting Linac RF SSPA; SSPA 10 kW

  • Lecture (Conference)
    CWRF2012,The Seventh CW and High Average Power RF Workshop, 07.-11.05.2012, Port Jefferson, NY, USA

Permalink: https://www.hzdr.de/publications/Publ-17189
Publ.-Id: 17189


Verminderung des Verblockungspotentials von Sumpfansaugsieben durch Korrosionsprodukte nach Kühlmittelverluststörfällen

Hoffmann, W.; Kryk, H.

Bei einem postulierten Kühlmittelverluststörfall (Loss of Coolant Accident LOCA) eines Druckwasserreaktors (DWR) kann die thermische Isolation (Mineralwolle) durch das austretende Dampf-Kühlmittelgemisch zerstört werden und das freigesetzte Material durch Ablagerung auf den Sumpfansaugsieben einen Druckverlust verursachen, der die Notkühlung beeinträchtigt. Im weiteren Verlauf bewirkt das borsäurehaltige Primärkühlmittel eine Korrosion von feuerverzinktem Stahleinbauten im Containment (überwiegend Gitterroste), deren feste Produkte bei Anlagerung an den Mineralwolleablagerungen zu einen kritischen Anstieg des Differenzdrucks über den Sumpfansaugsieben bis hin zur Blockade und dem Ausfall der Notkühlung führen können.
In der Laborversuchsanlage (KorrVA) wurde die Korrosion verzinkter Materialproben unterschiedlicher Größe und Geometrie bei verschiedenen Anströmbedingungen des borsäurehaltigen Kühlmittels unter störfallähnlichen Bedingungen untersucht. Der in der Nachkühlphase durch die Fallhöhe des Leckstrahls verursachte Impact auf die Materialprobe wurde mittels Flachstrahldüse nachgebildet. Für diese generischen Untersuchungen wurden die Prozesse Faseablagerung auf einem Sieb von dem der Bildung und Einlagerung der Korrosionsprodukte getrennt, indem Kühlmittelstrom erst nach Ausbildung des Faserbetts auf die Korrosionsprobe gerichtet wurde.
Ausgehend von dem festgestellten Mechanismus einer strömungsinduzierten Korrosion des Zinks im Leckstrahl, die verbunden ist mit der Änderung wasserchemischer Parameter wie einem Anstieg des pH-Werts und der Bildung von gelöstem Zink, kann nach schneller Freilegung des Stahls im unmittelbaren Leckstrahlbereich als Korrosionsprodukt Rost entstehen und bis hin zu einer Verblockung des Faserbetts führen. Ausgehend von den Experimenten ergaben sich zwei grundsätzliche Möglichkeiten diese Gefahr zu vermindern, indem die Freilegung der blanken Stahloberfläche zeitlich zu verzögert oder möglichst verhindert wird. In zwei Versuchsreihen mit verzinkten Flachstahlproben wurde gezeigt, dass sowohl ein zusätzliches Angebot an im Kühlmedium getauchter Oberfläche als auch eine Anhebung des pH-Werts den Anstieg des Differenzdrucks und speziell die Ablagerung von Korrosionsprodukten des Eisens am Faserbett vermindern. Als bester Weg erwies sich die Anhebung des pH-Werts durch eine ausreichende Menge an Borax. Weil im Leckstrahl die Korrosionsbeanspruchung von Gitterrosten, bedingt durch deren Geometrie, sich von der einer Flachstahlprobe unterscheidet, wurden die Ergebnisse an reellen Proben verzinkter Gitterroste in der Versuchsanlage überprüft.

Keywords: LOCA; corrosion products; zinc; sump screen clogging

  • Lecture (Conference)
    Jahrestagung Kerntechnik 2012, 22.-24.05.2012, Stuttgart, Deutschland
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2012, 22.-25.05.2012, Stuttgart, Deutschland
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-17188
Publ.-Id: 17188


Physics of spectral and geometric singularities on the WKB thresholds of Standard and Helical MRI

Kirillov, O.; Stefani, F.

The magnetorotational instability (MRI) triggers turbulence and enables outward transport of angular momentum in hydrodynamically stable rotating shear flows, e.g., in accretion disks. What laws of differential rotation are susceptible to the destabilization by axial, azimuthal, or helical magnetic field? How the standard, helical and azimuthal versions of MRI are related to each other? The answer to these questions, which is vital for astrophysical and experimental applications, inevitably leads to the study of spectral and geometrical singularities on the instability threshold. These singularities provide a connection between seemingly discontinuous stability criteria and thus explain several paradoxes in the theory of MRI that were poorly understood since the 1950s. On the other hand, the singular geometry of the instability threshold is a powerful tool for parametric optimization that predicts, e.g., how close to the Kepler or solid body rotation profiles the instability threshold can be moved by varying the magnetic field configuration, velocity, and material properties of the liquid. Using the local WKB approximation we study the thresholds of standard and helical MRI for axi- and non-axisymmetric perturbations, their extrema and the links between them in the fully viscous and resistive setting. We discuss the connection between standard and helical MRI via a spectral exceptional point as well as the behavior of the helical MRI threshold both in the inductionless approximation when the magnetic Prandtl number (Pm) tends to zero and in case when it is small but finite. We demonstrate that the Liu limit for the Rossby number at the onset of HMRI slightly increases when Pm is not vanishing and find its ultimate value.

Keywords: Magnetorotational instability; WKB; azimuthal magnetic field; non-axisymmetric perturbations; Rossby number; Liu limit

  • Invited lecture (Conferences)
    Rotational dynamics for planetary and stellar applications, 29.-30.05.2012, Marseille, France

Permalink: https://www.hzdr.de/publications/Publ-17187
Publ.-Id: 17187


Exceptional and diabolical points in stability questions

Kirillov, O.

“I never satisfy myself until I can make a mechanical model of a thing” - guided by this motto of Lord Kelvin we would like to invite a reader to look at some modern concepts such as a non-Hermitian Hamiltonian, exceptional points, the geometric phase, and PT -symmetry, through the prism of the classical mechanics and stability theory. Mathematical and historical parallels discussed in the paper evidence that positions occupied by the non-Hermitian physics and non-conservative mechanics are closer to each other than one might expect.

Keywords: Non-Hermitian Hamiltonian; exceptional point; stability; non-conservative system; modulational instability

Permalink: https://www.hzdr.de/publications/Publ-17186
Publ.-Id: 17186


Experimental Studies On Sub-Cooled Boiling In A 3x3 Rod Bundle

Barthel, F.; Franz, R.; Krepper, E.; Hampel, U.

With the continuing interest in modeling of boiling heat transfer in complex geometries, such as rod bundles, dedicated experiments with advanced instrumentation are essential. Within a larger cooperative project on boiling flow and heat transfer in rod bundle geometries HZDR has developed and setup an experimental rod bundle facility where first experiments were conducted. The facility is a flow loop with a vertical rod bundle test section operated with a refrigerant coolant (RC318). The test section is 1078 mm long and equipped with an electrically heated 3 × 3 rod bundle. The heating pattern is constant along the height and heating is concentrated in the central rod with 98.5% of total heating power. Experiments can be conducted with variable liquid flow rates, heating power and sub-cooling. Single phase flow in the bundle was studied with DPIV measurements. For void fraction measurement we operate both a gamma ray densitometer as well as high-speed X-ray tomography. In this paper we present first experimental studies with both void measurement techniques.

Keywords: sub-cooled boiling; electron beam X-ray CT; rod bundle experiment

  • Lecture (Conference)
    CFD4NRS-4, 10.-12.09.2012, Daejeon, Korea
  • Contribution to proceedings
    CFD4NRS-4, 10.-12.09.2012, Daejeon, Korea
    Proceedings of the CFD for Nuclear Reactor Safety Applications (CFD4NRS-4) Workshop

Permalink: https://www.hzdr.de/publications/Publ-17185
Publ.-Id: 17185


First Experience at Elbe with the new 1.3 GHz CWRF-Power System equipped with 10 kW Solid State Amplifiers

Büttig, H.; Arnold, A.; Büchner, A.; Justus, M.; Kuntzsch, M.; Lehnert, U.; Michel, P.; Schurig, R.; Staats, G.; Teichert, J.

With the expansion of the radiation source ELBE, a centre for high power radiation sources is being built until 2014 at the Helmholtz Zentrum Dresden Rossendorf. One part of this program is to double the beam current of the ELBE LINAC. In January 2012 each of the 10 kW CW klystrons, used to operate the superconducting cavities of ELBE since 2001, had been replaced by a pair of 10 kW solid state amplifiers. The paper gives an overview on the activities around this project and the first experience with the new RF-system.

Keywords: ELBE RF; 1.3 GHz Solid State Power Amplifier; 10kW, 1.3 GHz SSPA; LDMOS PA 10kW at 1300MHz; ELBE RF Upgrade; BRUKER SSPA 10kW at 1300MHz

  • Open Access Logo Contribution to proceedings
    IPAC2012 - International Particle Accelerator Conference 2012, 20.-25.05.2012, New Orleans, USA
    Proceedings of IPAC2012, THPPC053: Joint Accelerator Conference Website (JACoW)., 978-3-95450-115-1, 3407

Permalink: https://www.hzdr.de/publications/Publ-17183
Publ.-Id: 17183


Modelling and esxperimental databases on poly-dispersed bubbly flows

Lucas, D.; Krepper, E.; Beyer, M.; Szalinski, L.

In dispersed flows particle sizes play an important role on the evolution of the flow along the flow path. Flow situations where the dispersed phase is liquid or gas as e.g. in dispersed oil-water or in bubbly flows can frequently be found. Coalescence and breakup become important as soon as the dispersed phase volume fraction exceeds several percent. In the result a spectrum of bubble or drop sizes occurs. The momentum exchange between the continuous and dispersed phase strongly depend on the bubble respective drop size, i.e. the resulting velocity fields differ for particles with different sizes. In following the discussion is focused on poly-dispersed bubbly flows, but the phenomena are similar for dispersed oil-water flows in which oil or water may be the dispersed phase, respectively.

The momentum transfer between bubbles and the continuous liquid phase is usually considered by so-called bubble forces. The most important ones are drag, virtual mass, lift, turbulent dispersion and wall forces. All of them depend on the bubble size and the lateral lift force even may change its sign depending on the bubble size. This was found experimentally for single bubbles rising in a laminar linear shear flow [1] and confirmed by several DNS simulations. Lucas & Tomiyama showed that the change of the sign of the lift force predicted by the correlation obtained by Tomiyama et al. even holds turbulent poly-dispersed for air-water and steam flows with high gas volume fraction. In case of air-water flows at ambient conditions the critical bubble diameter for the change is 5.8 mm. In consequence for modeling poly-dispersed flows in a liquid shear flow, e.g. in a vertical tube a spatial separation of large and small bubbles occur and local bubble size distributions differ clearly from tube cross section averaged ones. For this reason the evolution of poly-dispersed flows is characterized by a complex interaction between local and bubble size effects.
To consider the different behavior of particles with different sizes the so-called Inhomogeneous MUSIG-Model was developed jointly by HZDR and ANSYS. It is implemented in the CFX-code and allows the representation of the dispersed phase by a (small) number of velocity groups (phases) and larger number of bubbles size classes (MUSIG groups).

For the validation of the model concept and appropriate closure models experimental data in high resolution in space and time are required. Vertical pipe flow is a suitable configuration to investigate such flows. Detailed data were obtained in several experiments at HZDR using the wire-mesh sensor technique. A high quality data base was established from experiments in a 8 m long pipe with an inner diameter of 195.3 mm. Measurements were done for 48 combinations of air and water superficial velocities varying from 0.04 m/s to 1.6 m/s for liquid and 0.0025 m/s to 3.2 m/s for air. Data were obtained for 12 different L/D in case of gas injection via 1 mm orifices in the pipe wall and for 6 different L/D in case of 4 mm orifices. From the raw data three-dimensional matrices of the instantaneous void fraction were obtained by calibration. These matrices were used for the calculation of time averaged data as: radial gas volume fraction profiles, bubble size distributions, radial volume fraction profiles decomposed according to the bubble size, interfacial area density and from a cross correlation between two sensors also the radial profiles of the gas velocity. All data are checked regarding their consistency. An estimation of errors was done by comparing the gas volume flow rates obtained from the measured radial profiles of void fraction and gas velocity with the setting values.

Within the same experimental setup also databases for condensing and evaporation steam-water flows were generated. They allow to validate the transferability of the models for different combinations of fluids. All these data bases are used in house and by different groups worldwide to develop, test and validate closure models for bubble forces and coalescence and break-up. At HZDR a standard model combining the closure models most suitable for wide range of flow conditions was developed. It will now be improved step by step.

Keywords: bubbly flow; model; CFD; poly-dispersed; pipe flow

  • Contribution to proceedings
    5th Latin American Workshop Applied to the Oil and Gas Industry, 10.-11.07.2012, Rio de Janeiro, Brasilien
  • Lecture (Conference)
    5th Latin American Workshop Applied to the Oil and Gas Industry, 10.-11.07.2012, Rio de Janeiro, Brasilien

Permalink: https://www.hzdr.de/publications/Publ-17182
Publ.-Id: 17182


Quantitative data from ultra-fast electron beam X-ray computer tomography measurements

Lucas, D.; Hoppe, D.; Banowski, M.; Hampel, U.; Barthel, F.; Sprewitz, U.; Beyer, M.

The ultra-fast electron beam X-ray computer tomography was developed during last years at HZDR and turned out to be a suitable measuring technique to get new insights into two-phase flow structures. The aim of new experiments done at a vertical pipe with an inner diameter of about 54 mm and a length of 4 m (usable for experiments) was to obtain quantitative data suitable for CFD-code development and validation. The pipe was built up using Titanium. This allows a wall thickness of only 1.6 mm which is enough for steam-water experi¬ments which will be carried out at a pressure up to 6.5 MPa. To generate the X-rays an electron beam is focused on a circular two-step target. This electron beam is deflected very fast and moves over the target resulting in a fast moving X-ray source. The X-rays pass through the object to be investigated and are registered by an arc of detectors. A tomographic reconstruction algorithm provides images of the attenuation distribution in the cross section of the object which is interpreted as density distribution. This allows the determination of the gas- liquid interfacial structure inside the considered object. Measurements were done with a measuring frequency of 2500 images/s and measuring time was 10 s. Air-water and steam-water flows were investigated for different combinations of gas and liquid flow rates and different distances from the gas injection.
The tomographic reconstruction provides 2 3D matrices of gray-scale values since the two-step target allows measurement in two planes with an axial distance of about 11 mm. Cross-correlation algorithms are applied to obtain the information on local gas velocities. Due to noise and artifacts a binarisation of the data seems to be necessary. Using a simple threshold method may cause small bubble to go missing. For this reason another method basing on gradients was developed. The presentations discusses this method and the present status of this new measuring technology in respect to quality and uncertainties of the quantitative data obtained as e.g. local void fraction and bubbles sizes.

Keywords: two-phase; measuring technique; X-ray; tomogrphy; pipe flow; bubble

  • Lecture (Conference)
    50th European Two-Phase Flows Group Meeting 2012, 16.-18.05.2012, Udine, Italy

Permalink: https://www.hzdr.de/publications/Publ-17181
Publ.-Id: 17181


Geology and architecture of the Norra Kärr Zr-REE deposit, Southern Sweden

Atanasova, P.; Leijd, M.; Gutzmer, J.

The Norra Kärr rare metal deposit in Southern Sweden represents one of the largest resources of rare earth elements (REE) in Europe. The deposit is hosted by a metamorphosed and deformed peralkaline nepheline syenite intrusion, which covers an area of 350m by 1100m. This intrusion is situated within a suite of Proterozoic gneisses and granites referred to as the Växjö Granite. The Växjö Granite belongs to the Trans-Scandinavian Igneous belt (1.85-1.65 Ga); the age of the peralkaline intrusion is rather poorly constrained at about 1545 ± 61 Ma (Blaxland 1977, recalculated by Welin 1980). Gross magmatic layering and orientation of early deformation fabrics suggest the intrusion was emplaced as a sill within the granitic basement (Rankin 2011). The granitoid rocks close to the contact to the peralkaline intrusion exhibit signs of fenitization (Adamson 1944, Eckermann 1968).

The Norra Kärr nepheline syenite and the surrounding basement have been deformed by weak to moderate N-S directed compression (Rankin 2011). This late-stage fold event has produced rhombic bulging and necking of the intrusion. The body is preserved within an overturned synformal hinge suggesting potential for other nepheline syenite bodies within the region. The intrusion has undergone not only modification of its shape by 3 phases of folding, but also possible transport of the body from its original emplacement locus by both N-S movement and E-vergent movement. In addition, the overprinting of the regional NNE-trending structural corridor by later episodes of extensional faulting also obscures the original geometry.

The Norra Kärr REE mineralization is notably enriched in the coveted heavy REE (HREE) and has been granted by the Geological Survey of Sweden a “national interest” status. The intrusion was first discovered by the Swedish Geological Survey in the earlier year of the 20th century and first described by A. E. Törnebohm in 1906. Since its discovery it has been explored – and on a small scale exploited - for nepheline, Zr and Hf. Since August 2009 Tasman Metals pursues an aggressive exploration program that focuses on rare metals mineralization, in particular HREE, in the intrusion. Currently, resources in the deposit are 41.6 Mt @ 0.57 % TREO with 51 % HREO/TREO and 1.7 % ZrO2 (indicated) and 16.5 Mt @ 0.64 % TREO with 49% HREO/TREO and 1.7 % Zr2O (inferred).

The lithotypes that comprise the intrusion are mostly identified by local names only; they share an agpaitic composition but their spatial and genetic relationship of the lithotypes remains unclear at present. The most common lithotype present is referred to as grennaite, best described as a fine to medium grained meta-syenite consisting of alkali feldspar, nepheline, aegirine, natrolite, eudialyte and catapleiite (Adamson 1944, Blaxland 1977). Less common lithotypes include lakarpite (arfvedsonite-albite nepheline meta-syenite), pulaskite (microcline-arfvedsonite-albite nepheline meta-syenite) and kaxtorpite (eckermannite-microcline-aegirine-pectolite nepheline meta-syenite). Exploration has revealed that much of the rare metal mineralization is associated with pegmatitic and migmatitic intervals within the complexly zoned intrusion, suggesting an important influence of (fluid-induced?) recrystallization and remobilization on the character and distribution of rare metal mineralization. Mineralogical studies have shown REE bearing minerals to include eudialyte group minerals and very minor mosandrite and cerite. The Zr-silicates catapleiite and eudialyte host the majority of the zirconium.

Keywords: REE; rare earth elements; zirconium; deposit; alkaline; rare metals

  • Poster
    Geochemistry of mineral deposits, 15.-20.07.2012, Andover, NH, United States

Permalink: https://www.hzdr.de/publications/Publ-17180
Publ.-Id: 17180


Numerical Simulation of Horizontal Two-Phase Flow Experiments Using an Morphology Detection Model

Höhne, T.; Darlianto, D.; Lucas, D.

Eine geschichtete Zweiphasenströmung liegt z.B. im Heißstrang eines Kernreaktors bei einem Kühlmittelverluststörfall vor. Ein Problem der Simulation von Zweiphasenströmungen mit CFD-Codes besteht darin, dass lokal unterschiedliche Morphologien der Phasengrenzen auftreten können. Die disperse und die kontinuierliche Form der Gas- und Fluidphase werden in der Modellierung jeweils als separate Phasen behandelt. Die disperse Phase liegt in Form von Wassertröpfchen oder Gasblasen vor. An der Phasengrenze zwischen kontinuierlichen Phasen (d.h. in der Simulation wird die Phasengrenze aufgelöst) müssen andere Schließungsmodelle, z.B. für den Impulsaustausch, angewendet werden als an einer Grenze zwischen kontinuierlicher und disperser Phase. Bisher war das nicht möglich, da die Information über die jeweils vorliegende Strömungsmorpholgie im CFD-Code nicht vorlag. Deshalb wurde in enger Zusammenarbeit mit dem Codeentwickler ANSYS ein Modell zur besseren Beschreibung der wirkenden physikalischen Gesetze bei Zweiphasenströmungen in Abhängigkeit der Strömungsmorphologie (AIAD= Algebraic Interfacial Area Density Modell) entwickelt, erprobt und in den CFD-Code CFX implementiert. Validierungsrechnungen für das AIAD-Modell wurden für Experimente am Heißstrangmodell an TOPFLOW bzw. dem TOPFLOW_PTS Versuchsstand sowie für Schwallströmungen und dem stationären hydraulischen Sprung im horizontalen Strömungskanal HAWAC durchgeführt und zeigten durchweg gute Ergebnisse. Für die Zukunft ist eine verbesserte Beschreibung der Turbulenz an der Phasengrenzfläche geplant.

Keywords: TOPFLOW PTS HAWAC AIAD CFX

  • Invited lecture (Conferences)
    ANSYS Conference & dem 30. CADFEM Users´ Meeting, 24.-26.10.2012, Kassel, Deutschland
  • Contribution to proceedings
    ANSYS Conference & dem 30. CADFEM Users´ Meeting, 24.-26.10.2012, Kassel, Deutschland
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-17179
Publ.-Id: 17179


Development and validation of a morphology detection algorithm (AIAD) for horizontal two phase flows

Höhne, T.

In order to improve the understanding of counter-current two-phase flows and to validate new physical models, CFD simulations of 1/3rd scale model of the hot leg of a German Konvoi Pressurized Water Reactor (PWR) with rectangular cross section was performed. Selected counter-current flow limitation (CCFL) experiments at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) were calculated with ANSYS CFX 12.1 using the multi-fluid Euler-Euler modeling approach. The transient calculations were carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a SST turbulence model for each phase.

In the simulation, the surface drag was approached by a new correlation inside the Algebraic Interfacial Area Density (AIAD) model. The AIAD model allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value.

A comparison with the high-speed video observations shows a good qualitative agreement. The results indicated that quantitative agreement of the CCFL characteristics between calculation and experimental data was obtained. To validate the model and to study scaling effects CFD simulations of the CCFL phenomenon in a full scale PWR hot leg of the UPTF test facility were performed. Also these results indicated a good agreement between the calculation and experimental data. The final goal is to provide an easy usable AIAD framework for all ANSYS CFX users, with the possibility of the implementation of their own correlations.

Keywords: AIAD CCFL CFX PWR UPTF ANSYS

  • Lecture (Conference)
    5th Latin American CFD Workshop Applied to the Oil and Gas Industry, 10.-11.07.2012, Rio de Janeiro, Brasilien
  • Contribution to proceedings
    5th Latin American CFD Workshop Applied to the Oil and Gas Industry, 10.-11.07.2012, Rio de Janeiro, Brasilien
    CD-ROM
  • Open Access Logo Petrobras Technical Bulletin (2016)

Permalink: https://www.hzdr.de/publications/Publ-17178
Publ.-Id: 17178


High energy CPA-free picosecond Yb:YAG amplifier

Loeser, M.; Siebold, M.; Roeser, F.; Schramm, U.

We report on a CPA free picosecond MOPA system consisting of a fs Yb:KGW oscillator and 2 subsequent amplifiers using Yb:YAG active mirrors. A maximum pulse energy of 35mJ at 10Hz repetition rate was achieved.

Keywords: Lasers, diode-pumped; Lasers Ytterbium; Laser amplifiers

  • Poster
    Advanced Solid-State Photonics (ASSP), 29.01.-03.02.2012, San Diego, USA
  • Lecture (others)
    Disk Laser Workshop, 14.-15.05.2012, Stuttgart, Germany

Permalink: https://www.hzdr.de/publications/Publ-17177
Publ.-Id: 17177


High-energy laser amplifiers using ultra-broad emitting Yb-doped materials

Siebold, M.; Loeser, M.; Roeser, F.; Uecker, R.; Koerner, J.; Hein, J.; Hornung, M.; Keppler, S.; Kaluza, M.; Schramm, U.

High-energy laser amplifiers using Yb-doped gain media often show reduced efficiencies especially when operating at ultra-short pulses. We summarize techniques to improve storage and extraction efficiencies of Yb-based laser amplifiers.

Keywords: Lasers diode-pumped; Lasers Ytterbium; Laser amplifiers

  • Invited lecture (Conferences)
    Advances in Optical Materials (AIOM), 01.-03.02.2012, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-17176
Publ.-Id: 17176


New Aspects in Modelling Counter-Current Flow Phenomena Using a Morphology Detection Algorithm

Höhne, T.

Counter current flow was successfully simulated in the Hot Leg Channel.
A new surface drag model inside the morphology detection algorithm AIAD was introduced, it further improves the physics.
The qualitative structure of the flow morphology is similar to the one observed in the experiment (slug flow regime).
The calculated quantitative CCFL characteristics & water levels inside the hot leg channel were in an agreement with the experiments.
CFD calculations of 1:1 scaled UPTF CCFL experiments show very promizing results.
The effect of turbulence parameters near the free surface has to be studied in future.
Validation of the AIAD model is going on – Official release of the AIAD framework in CFX is on the way.

Keywords: CCFL AIAD CFX Hot Leg Channel

  • Lecture (Conference)
    Multiphase Flow Conference and Short Course: Simulation, Experiment and Application, 13.-14.06.2012, Dresden, Deutschland
  • Contribution to proceedings
    Multiphase Flow Conference and Short Course: Simulation, Experiment and Application, 13.-14.06.2012, Dresden, Deutschland
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-17175
Publ.-Id: 17175


Development and validation of a morphology detection algorithm (AIAD)

Höhne, T.

Counter current flow was successfully simulated in the Hot Leg Channel.
A new surface drag model inside the morphology detection algorithm AIAD was introduced, it further improves the physics.
The qualitative structure of the flow morphology is similar to the one observed in the experiment (slug flow regime).
The calculated quantitative CCFL characteristics & water levels inside the hot leg channel were in an agreement with the experiments.
CFD calculations of 1:1 scaled UPTF CCFL experiments show very promizing results .
The effect of turbulence parameters near the free surface has to be studied in future.
Validation of the AIAD model is going on – Official release of the AIAD framework in CFX is on the way.

Keywords: UPTF CCFL CFD Hot Leg Channel AIAD CFX

  • Lecture (Conference)
    AER Working Group C and G, 31.05.-01.06.2012, Paks, Ungarn

Permalink: https://www.hzdr.de/publications/Publ-17174
Publ.-Id: 17174


Ultrasonic flow measurements in a model of a Czochralski puller

Cramer, A.; Pal, J.; Gerbeth, G.

An experimental study of the buoyancy-induced flow in a model of a Czochralski crystal growth system was conducted. Ultrasonic velocimetry was used to measure fluid velocities. To have similar thermal boundary conditions as in an industrial growth facility, a double-walled glass crucible flown through by a heating fluid was chosen to hold the fluid. Similarity of the heat transfer conditions was achieved by selecting a liquid metal as the fluid under investigation, which was the ternary alloy GaInSn having a Prandtl number of 0.021. Because of the double-walled crucible, measurements through the container wall are difficult if ever possible. Since the availability of relatively short ultrasonic transducers it is practicable to have the sensor immersed into the fluid. Measurements of the radial velocity component shortly below the melt surface across the entire diameter of the crucible at various azimuthal angles reveal the complex flow structure of natural convection in a Czochralski crucible. As it is not to be expected to grow high quality mono-crystalline crystals from such a non-axisymmetric flow, rotating magnetic fields (RMF) are often proposed to render the flow more axisymmetric. This paper also addresses the question what happens to the buoyancy-driven flow when such an RMF is applied.

Keywords: Czochralski crystal growth; Rayleigh-Benard convection; ultrasonic flow measurement; electromagnetic stirring

Permalink: https://www.hzdr.de/publications/Publ-17173
Publ.-Id: 17173


Numerical simulation and experimental verification of the DC magnetic field effect on the fluid flow in a continuous casting mould

Miao, X.; Timmel, K.; Lucas, D.; Eckert, S.; Gerbeth, G.

This paper presents numerical and experimental investigations with respect to the fluid flow in the continuous casting process under the influence of an external DC magnetic field. According to the concept of the electromagnetic brake (EMBR) the impact of a DC magnetic field on the outlet flow from the submerged entry nozzle (SEN) has been studied up to Hartmann numbers of about 400. Numerical calculations were performed by means of the software package CFX with an implemented RANS-SST turbulence model. The non-isotropic nature of the MHD turbulence was taken into account by specific modifications of the turbulence model. The numerical results were validated by flow measurements carried out in a small-scale mockup using the eutectic alloy GaInSn. The comparison between our numerical calculations and the experimental results displays a very well agreement. The magnetic field causes a deflection of the jet and decreases its exit angle from the nozzle ports. An elongation of the jet cross section can be observed along the magnetic field direction. A significant return flow occurs in the adjacent regions of the jet. Specific vortices are formed with axes being aligned with the magnetic field direction, which is typical for quasi-two-dimensional magneto-hydrodynamic flows. Likewise, the results did not confirm the expectation that the use of the DC magnetic field induces a general reduction of the velocity fluctuations all over the mould region. Actually, under certain conditions the application of a horizontal magnetic field may cause intense, non-steady and non-isotropic flow structures. Another important result of our study is the feature that the electrical boundary conditions have a serious influence on the mould flow just as it is exposed to an external magnetic field.

Keywords: continuous casting; liquid metal model; electromagnetic brake; MHD-turbulence; RANS-SST turbulence model

  • Lecture (Conference)
    5th International Congress on the Science and Technology of Steelmaking 2012, 01.-03.10.2012, Dresden, Deutschland
  • Contribution to proceedings
    5th International Congress on the Science and Technology of Steelmaking 2012, 01.-03.10.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17172
Publ.-Id: 17172


Flow following sensor particles – validation and macro-mixing analysis in a stirred fermentation vessel with a highly viscous substrate

Reinecke, S.; Kryk, H.; Hampel, U.; Deutschmann, A.; Jobst, K.; Friedrich, E.

A group of flow following sensor particles was validated under real flow conditions in a highly viscous substrate in a 1000 L model fermenter vessel, equipped with a pitched blade impeller, which was operated at two different axial positions in an intermittent mixing regime. The neutrally buoyant sensor particles track basic hydrodynamic and process parameters, namely hydrostatic pressure (giving the axial position), temperature and acceleration. The sensors are connected to a measurement electronics, which is enclosed in a robust capsule that can resist the harsh conditions in an industrial mixing process. The results show that the sensor particles still reflect the flow conditions in the vessel qualitatively. Moreover, the sensor particle data allow estimation of macro-mixing parameters, such as circulation time distributions and average circulation times.

Keywords: Flow Follower; Sensor Particle; Autonomous Sensor; Macro-Mixing; Circulation Time; Parameter Tracking; Bio-substrate; Biogas; Bioreactor

Permalink: https://www.hzdr.de/publications/Publ-17171
Publ.-Id: 17171


Intelligente Sensorpartikel zur Prozessdiagnose in Mischbehältern

Reinecke, S.; Kryk, H.; Hampel, U.

Der Betrieb großer Anlagen und Behälter wird von dem Problem begleitet, dass darin ablaufende verfahrens- und energietechnische Prozesse aufgrund erschwerter oder unmöglicher messtechnischer Zugänglichkeit nicht genügend beschrieben und überwacht werden können. Die Installation von lokal installierten Sonden mit Kabelverbindungen ist in großen Behältern, wie Chemie- und Bioreaktoren, Fermentern oder Schüttgutbehältern, oft nicht realisierbar oder unerwünscht. Zudem sind bildgebende Messverfahren, wie Kameras oder Tomografiesysteme, auf Grund der trüben Medien und der Behälterabmessungen von mehreren Metern meist nicht anwendbar.
Der Einsatz intelligenter Strömungsfolger und autonomer Sensortechnologien ermöglicht die messtechnische Erfassung verteilter Parameter und gewinnt deshalb zunehmend an Bedeutung für Anwendungen in der Prozessindustrie [1].
Aus diesem Grund wurde am HZDR das Konzept autonomer Sensorpartikel entwickelt, welche als auftriebsneutrale Strömungsfolger in großen Behältern, wie Biogasfermentern, eingesetzt werden können und dabei kontinuierlich Prozessparameter erfassen, speichern und diese nach Rückgewinnung der Partikel aus dem Prozess einem computergestützten Analysesystem zur Verfügung stellen [2].

  • Poster
    15. Köthener Rührer-Kolloquium, 14.06.2012, Köthen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17170
Publ.-Id: 17170


Autonome Sensorik

Reinecke, S.; Hampel, U.

Für eine effiziente Steuerung von Prozessen in verfahrenstechnischen Anlagen ist eine detaillierte räumliche und zeitliche Erfassung von Prozessparametern erforderlich, die jedoch mit herkömmlichen Messverfahren nicht realisiert werden kann. Als vollkommen neuen Lösungsansatz dazu wurde am HZDR ein autonomes Sensorpartikel entwickelt, welches als Strömungsfolger in großen Behältern, wie Biogasfermentern, eingesetzt werden könnte und somit kontinuierlich Prozessparameter erfasst, speichert und diese nach Wiedergewinnung des Partikels am Behälterauslass einem Analysesystem zur Verfügung stellt.

  • Industrielle Automation 1(2012)3, 43-43

Permalink: https://www.hzdr.de/publications/Publ-17169
Publ.-Id: 17169


Autonome Sensorik für große Prozessbehälter (AUTOSENS)

Reinecke, S.; Kryk, H.; Tschofen, M.

Für eine effiziente Steuerung von Prozessen in verfahrenstechnischen Anlagen ist eine detaillierte räumliche und zeitliche Erfassung von Prozessparametern erforderlich, die jedoch mit herkömmlichen Messverfahren nicht realisiert werden kann. Als vollkommen neuen Lösungsansatz dazu wurde am HZDR ein autonomes Sensorpartikel entwickelt, welches als Strömungsfolger in großen Behältern, wie Biogasfermentern, eingesetzt werden könnte und somit kontinuierlich Prozessparameter erfasst, speichert und diese nach Wiedergewinnung des Partikels am Behälterauslass einem Analysesystem zur Verfügung stellt.

Permalink: https://www.hzdr.de/publications/Publ-17168
Publ.-Id: 17168


Grain refinement by electromagnetic stirring and the impact on the mechanical properties of alsi-alloys

Räbiger, D.; Krößig, C.; Eckert, S.; Gerbeth, G.

This present study examines the directional solidification of AlSi7 alloys from a water cooled copper chill. A rotating magnetic field was used for melt agitation. Different magnetic field configurations were considered to demonstrate the impact of diverse flow conditions on the resulting microstructure and the mechanical properties. The solidified structure was evaluated in comparison to an unaffected solidified ingot. Measurements of the phase distribution, the grain size, the hardness and the tensile strength were performed. Our results reveal the potential of magnetic fields to control the grain size, the formation of segregation freckles and the mechanical properties. In particular, time–modulated rotating fields demonstrated their capability to homogenize both the grain size distribution and to improve the mechanical properties.

Keywords: rotating magnetic field; solidification; grain refinement; mechanical properties; AlSi alloys

  • Journal of Iron and Steel Research International 19(2012)Suppl. 1-1, 341-344
  • Poster
    7th International Conference on Electromagnetic Processing of Materials, 22.-26.10.2012, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-17167
Publ.-Id: 17167


Flow control during solidification of AlSi-alloys by means of tailored ac magnetic fields

Zhang, Y.; Räbiger, D.; Vogt, T.; Eckert, S.; Gerbeth, G.

This paper presents an experimental study which in a first stage is focused on obtaining quantitative information about the isothermal flow field exposed to various magnetic field configurations. Melt stirring has been realized by utilizing time-modulated AC magnetic fields in different variants. We consider time-modulated fields or combinations of traveling magnetic fields (TMF) and rotating magnetic fields (RMF). In a second step solidification experiments are carried out to verify the effect of a certain flow field on the solidification process. Our results demonstrate that the melt agitation using modulated magnetic fields offers a considerable potential for a well-aimed modification of casting properties by an effective control of the flow field.

Keywords: rotating magnetic field; travelling magnetic field; modulated fields; solidification; AlSi alloys

  • Journal of Iron and Steel Research International 19(2012)Suppl. 1-1, 574-577
  • Poster
    7th International Conference on Electromagnetic Processing of Materials, 22.-26.10.2012, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-17166
Publ.-Id: 17166


Inertial waves occurring in a liquid metal column due to pulsed excitation by a rotating magnetic field

Räbiger, D.; Vogt, T.; Franke, S.; Czarske, J.; Eckert, S.; Gerbeth, G.

We present an experimental study concerning the flow inside a liquid metal column exposed to a pulsed rotating magnetic field. This paper is aimed at highly resolved, quantitative velocity measurements in the eutectic GaInSn alloy. A novel ultrasound Doppler system was used two measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane. It employs an array of 25 transducer elements allowing a fast electronic traversing with concurrently high spatial and temporal resolution. The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures. The results demonstrate that the arising flow structure depends sensitively on the frequency of the RMF pulses. A maximum intensity of a periodic meridional flow can be observed, if the corresponding pulse frequency fP relates to the eigenperiod of the respective inertial mode in a developed regime. The electromagnetic stirring method that uses a modulated RMF offers considerable potential to enhance the stirring efficiency and to optimize the properties of castings by a well-aimed flow control during solidification.

Keywords: rotating magnetic field; electromagnetic stirring, inertial waves; flow control

  • Lecture (Conference)
    7th International Conference on Electromagnetic Processing of Materials, 22.-26.10.2012, Beijing, China
  • Journal of Iron and Steel Research International 19(2012)Suppl. 1-1, 82-85

Permalink: https://www.hzdr.de/publications/Publ-17165
Publ.-Id: 17165


Visualization of the flow in a mold of continuous casting by contactless inductive flow tomography and mutual inductance tomography

Wondrak, T.; Eckert, S.; Gerbeth, G.; Stefani, F.; Timmel, K.; Peyton, A. J.; Terzija, N.; Yin, W.

The flow structure in the mold of a continuous caster has a great influence on the quality of the produced steel. Conventional flow measurement techniques are prevented by the high temperature of the liquid steel. For a physical model of the continuous casting process using a low-melting point liquid metal, we present combined measurements of the flow in the mold by Contactless Inductive Flow Tomography (CIFT), and of the conductivity distribution in the submerged entry nozzle by Mutual Inductance Tomography (MIT). In addition, we summarize experiments with a magnetic stirrer around the submerged entry nozzle and its effects on the flow in the mold. Some new developments towards a robust implementation of CIFT at a real caster, including the use of pickup coils and gradiometric probes, are also discussed.

Keywords: continuous casting; flow measurement; contactless inductive flow tomography

  • Lecture (Conference)
    5th International Congress on the Science and Technology of Steelmaking 2012, 01.-3.10.2012, Dresden, Germany
  • Contribution to proceedings
    5th International Congress on the Science and Technology of Steelmaking 2012, 01.-3.10.2012, Dresden, Germany
  • Steel Research International 85(2014)8, 1266-1273
    DOI: 10.1002/srin.201300075

Permalink: https://www.hzdr.de/publications/Publ-17164
Publ.-Id: 17164


Flow pattern formation in a liquid metal column by pulsed excitation of a rotating magnetic field

Räbiger, D.; Vogt, T.; Franke, S.; Czarske, J.; Eckert, S.; Gerbeth, G.

We present an experimental study concerning measurements of the flow inside a liquid metal column exposed to a pulsed rotating magnetic field. A novel ultrasound Doppler system was used to measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane. It employs an array of 25 transducer elements allowing a fast electronic traversing with concurrently high spatial and temporal resolution. The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures.

Keywords: rotating magnetic field; inertial waves; liquid metal

  • Lecture (Conference)
    The 23rd International Congress of Theoretical and Applied Mechanics, 19.-24.08.2012, Beijing, China
  • Contribution to proceedings
    The 23rd International Congress of Theoretical and Applied Mechanics, 19.-24.08.2012, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-17163
Publ.-Id: 17163


Experimental Modelling of the Impact of a DC Magnetic Field on the Melt Flow in a Continuous Casting Mould

Timmel, K.; Wondrak, T.; Röder, M.; Stefani, F.; Eckert, S.; Gerbeth, G.

This paper describes experimental investigations of flow structures and related transport processes in the continuous casting mould under the influence of an external DC magnetic field at laboratory scale. Experimental results will be presented here which have been obtained using a physical model (mini-LIMMCAST) operating with the low melting point alloy GaInSn. According to the concept of the electromagnetic brake the impact of a DC magnetic field on the outlet flow from the Submerged Entry Nozzle (SEN) has been studied up to Hartmann numbers of about 400. The Ultrasound-Doppler-Velocimetry (UDV) was applied for measurements of the flow pattern in the mould. Local conductivity anemometers were used to measure the turbulent quantities of the flow. The effect of the magnetic field on the flow structure turned out to be manifold and rather complex. The magnetic field causes a deflection of the jet, at which the respective exit angle from the nozzle ports becomes more flat. Thus, both the penetration depth of the discharging flow into the lower part of the mould and the impinging velocity of the jet onto the side wall are reduced. A significant return flow occurs in the adjacent regions of the jet. Specific vortices are formed with axes being aligned with the magnetic field direction. Such vortical structures are typical for quasi-two-dimensional magneto-hydrodynamic (MHD) flows. The flow measurements do not manifest a general braking effect which would be expected as an overall damping of the flow velocity and the related fluctuations all-over the mould volume. Variations of the wall conductivity showed a striking impact on the resulting flow structures.

Keywords: continuous casting; liquid metal model; electromagnetic brake; ultrasonic flow measurement; potential probes

  • Lecture (Conference)
    7th International Conference on Electromagnetic Processing of Materials (EPM2012), 22.-26.10.2012, Peking, China
  • Journal of Iron and Steel Research International 19(2012)Suppl. 1-2, 862-865

Permalink: https://www.hzdr.de/publications/Publ-17162
Publ.-Id: 17162


Flow determination in a model of continuous casting by combining contactless inductive flow tomography and mutual inductance tomography

Wondrak, T.; Stefani, F.; Gerbeth, G.; Timmel, K.; Eckert, S.; Klotsche, K.; Peyton, A. J.; Yin, W.; Terzija, N.

For a physical model of a continuous caster, we present results on the simultaneous measurements of the flow in the mould by the Contactless Inductive Flow Tomography (CIFT), and of the conductivity distribution in the submerged entry nozzle (SEN) by Mutual Inductance Tomography (MIT) for a two phase flow setup. Depending on the gas flow rate, various flow regimes in the SEN and in the mould are identified, among them pressure oscillations in the gas feeding system, transitions between double and single vortex flows, and transient single port ejections.
In addition we give a summary of an experimental campaign with a magnetic stirrer around the SEN and its effects on the flow in the mould. As expected and desired, the swirling flow leads to a stronger upward fluid motion along the walls. At the same time, however, the oscillatory character of the flow becomes stronger.
The paper concludes with some new developments for CIFT towards a robust measurement of the very small induced magnetic field using pickup coils which allow the application of CIFT in environments with high DC magnetic fields and strong noise.

Keywords: liquid metal; contactless inductive flow tomography (CIFT); electromagnetic inductance tomography (MIT); continuous casting

  • Lecture (Conference)
    6th International Symposium on Process Tomography, 25.-28.3.2012, Cape Town, South Afrika
  • Contribution to proceedings
    6th International Symposium on Process Tomography, 25.-28.3.2012, Cape Town, South Afrika

Permalink: https://www.hzdr.de/publications/Publ-17161
Publ.-Id: 17161


Simulation von Diffusions-Adsorptionsprozessen in natürlichem Gesteinsmaterial mit COMSOL Multiphysics.

Schikora, J.

Viele Länder innerhalb Europas, wie zum Beispiel Frankreich, Deutschland oder die Schweiz, produzieren einen (großen) Teil ihres Energiebedarfs über Kernkraft. Zwar hat Deutschland den Ausstieg aus der Atomenergie beschlossen, sodass perspektivisch
kein neuer radioaktiver Abfall aus Kraftwerken anfällt, trotzdem besteht auch danach die Notwendigkeit der Entsorgung von radioaktiven Stoffen aus der Industrie, Forschung und Medizin. Eine Option für die Entsorgung von radioaktiven Stoffen aus diesen Branchen sowie aus dem Betrieb und der Stilllegung von Kernkraftwerken ist die geologische Tiefenlagerung. Dafür geeignetes Wirtsgestein muss als Bestandteil des Multibarrierenkonzepts bestimmte Anforderungen erfüllen. Dieses Konzept soll den Einschluss der Kontaminanten über sehr lange Zeiträume garantieren, bis die Aktivität der Abfälle auf ein unbedenkliches Maß abgefallen ist. So sollte das gewählte Wirtsgestein eine möglichst geringe hydraulische Leitfähigkeit aufweisen. Der dominante Transportmechanismus ist dann die Diffusion und die Ausbreitung von Schadstoffen findet in solchen Gesteinen verlangsamt statt. Eine weitere Eigenschaft des Gesteins sollte seine Fähigkeit sein, den Transport von Kontaminanten durch Sorption zu retardieren.

Als potentielles Wirtsgestein für radioaktiven Abfall wird in der Schweiz der Opalinuston des Zürcher Weinlandes untersucht. Er weist die oben beschriebene Eigenschaft einer (sehr) geringen hydraulischen Leitfähigkeit (1·10-14 – 1·10-13 m/s) auf (Nagra, 2002). Es ist daher zu erwarten, dass der Transport von gelösten Substanzen innerhalb des Opalinuston durch Diffusion erfolgt. Des Weiteren bedingt der hohe Anteil an Tonmineralen in diesem Wirtsgestein eine gute Retardierung von Kontaminanten. Auch in Deutschland sind Tongesteine, wie der Opalinuston, Untersuchungsgegenstand im Zusammenhang mit der Lagerung von radioaktiven Abfällen und bei der Suche nach Alternativen zu Gorleben.

Der diffusive Transport spielt somit eine wichtige Rolle in Ausbreitungsrechnungen und damit in der Risikoabschätzung entsprechender untertägiger Deponien und Endlager. Für Langzeitsicherheitsanalysen werden neben einem guten Systemverständnis auch die Parameter der Transportgleichungen benötigt. Eine mögliche Vorgehensweise bei der Bestimmung von Transportparametern ist das Durchführen von Laborexperimenten. Die zugrundeliegenden Bilanzgleichungen lassen sich jedoch nicht in jedem Fall analytisch lösen. Es ist dadurch notwenig numerische Lösungsmethoden zu nutzen, zum Beispiel in Computersimulationen.

Gegenstand der vorliegenden Arbeit ist es, den Transport chemisch-toxischer und radioaktiver Kontaminanten in geologischen Formationen durch Simulation der Diffusions-Adsorptionsprozesse in natürlichem Gesteinsmaterial zu untersuchen. Als Simulationsumgebung kommt dabei COMSOL Multiphysics zum Einsatz. Sie nutzt zur numerischen Lösung von partiellen Differentialgleichungen die Methode der finiten Elemente.
Hauptziele, die in der vorliegenden Arbeit mit Hilfe der Modellbildung und Simulation der Transportprozesse erreicht werden sollen, sind die Nachrechnung vorhandener Experimente zur Parameterschätzung sowie prognostische Rechnungen zur Optimierung von Diffusionsexperimenten. Es sollen des Weiteren die Möglichkeiten des Simulationstools COMSOL Multiphysics zur effektiven Auswertung von komplexen, dreidimensionalen und anisotropen Daten aus zeitabhängigen Transportuntersuchungen evaluiert werden. Im Einzelnen werden die folgenden Teilaufgaben gelöst:

● Einarbeitung in COMSOL Multiphysics 4.2/4.2a, das Ergänzungsmodul Chemical Reaction Engineering sowie das Optimierungsmodul auch mit dem Ziel des weiteren Ausbaus der Nutzerkompetenz am Institut für Ressourcenökologie (vormals Institut für Radiochemie).

● Auswahl geeigneter Interfaces aus dem COMSOL Basismodul und ggf. dem Chemical Engineering Module für die Nachrechnung vorhandener Datensätze.

● Es sind ausgewählte explizite Diffusions- und Diffusions-Adsorptionsexperimente zu simulieren. Die Parameterbestimmung ist durch Datenabgleich zu gewährleisten. Darüber hinaus ist eine Auswahl alternativer Modelle zu testen und zu vergleichen; beispielsweise hinsichtlich der jeweils zu Grunde liegenden Gleichungen, der Porosität oder der Raum-Zeit-Skala.

● Für ein geplantes Diffusionsexperiment ist mittels prognostischer Rechnungen eine Optimierung der variablen Parameter vorzunehmen.

  • Diploma thesis
    TU Dresden, Fakultät Maschinenwesen, Professur Verfahrensautomatisierung, 2012
    105 Seiten

Permalink: https://www.hzdr.de/publications/Publ-17160
Publ.-Id: 17160


A controlled immobilization of His-tagged estrogen receptor hERa: Comparison study between the kinetics and morphology

Cherkouk, C.; Rebohle, L.; Gerlach, T.; Kunze, G.; Lenk, J.; Ou, X.; Pietzsch, J.; Skorupa, W.

A specific immobilization of macrobiomolecules on chip arrays is essential in order to increase the efficiency of biosensors as well as for the improvement of protein single studies. A comparison between a specific immobilization, like on nickel-nitrilotriacetic acid (Ni-NTA) matrix, and a covalent immobilization, like on amino self-assembling monolayers (SAMs), was investigated by using surface plasmon resonance (SPR). Whereas the number of the covalently immobilized estrogen receptors hER is higher than those of the specifically immobilized receptors, the affinity constant KD, using β-Estradiol as an analyte, is much higher in the case of the specific immobilization. This fact has been demonstrated by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The morphology of the covalent and specific immobilization of the His-tagged binding domain of the estrogen receptor (hERa-LBD-His10) confirms the SPR kinetics study.

Keywords: Estrogen receptor; Ni-NTA; His-tagged; SPR; AFM; SEM

  • Lecture (Conference)
    E-MRS 2012 SPRING MEETING, 14.-18.05.2012, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-17159
Publ.-Id: 17159


Impact of Soft Iron impellers in the Cadarache Dynamo experiment

Giesecke, A.; Stefani, F.; Gerbeth, G.

Numerical simulations of the kinematic induction equation are performed on a model configuration of the Cadarache von-Karman-Sodium dynamo experiment. The effect of a localized axisymmetric distribution of relative permeability that represents soft iron material within a flow of a conducting fluid is investigated. We observe a purely toroidal axisymmetric mode localized in the impeller disks which becomes dominant for sufficiently large permeability. In this limit, the toroidal mode is close to the onset of dynamo action with a (negative) growth-rate that is rather independent of the magnetic Reynolds number. We qualitatively explain this effect by paramagnetic pumping at the fluid/disk interface and propose a simplified analytical model that quantitatively reproduces numerical results. The crucial role of the high permeability disks for the mode selection in the Cadarache dynamo experiment cannot be inferred from computations that use idealized pseudo-vacuum boundary conditions.

Keywords: dynamo

  • Lecture (Conference)
    23rd International Congress of Theoretical and Applied Mechanics (ICTAM 2012), 19.-24.08.2012, Beijing, China
  • Contribution to proceedings
    23rd International Congress of Theoretical and Applied Mechanics (ICTAM 2012), 19.-24.08.2012, Peking, China
    Abstract Book, 978-988-16022-3-7

Permalink: https://www.hzdr.de/publications/Publ-17158
Publ.-Id: 17158


Femtosecond level electron bunch diagnostic at quasi-cw SRF accelerators: test facility ELBE

Gensch, M.; Helm, M.; Kaya, C.; Kuntzsch, M.; Lehnert, U.; Mamidala, V.; Michel, P.; Schneider, C.; Schurig, R.; Seidel, W.; Staats, G.; Al-Shemmary, A.; Schlarb, H.; Stojanovic, N.; Geloni, G. A.

Superconducting radiofrequency (SRF) accelerator technology allows to accelerate electron bunches not only in considerably longer bunch trains than is possible by normal conducting accelerator technology, but also in principle enables a mode of operation that can circumvent any macropulse scheme and provides relativistic electron bunches with real repetition rates scaling from the kHz to GHz regime [1, 2, 3, 4]. In this proceedings we discuss different approaches foreseen for online electron bunch diagnostic at the new femtosecond electron beamline of the superconducting cw RF accelerator ELBE [11]. In medium term we believe the concepts tested at the femtosecond beamline at ELBE are off great importance for various energy recovvery linac accelerators (ERL) coming online in the next few years [2, 4] as well as facilities like the European X-FEL [5] and FLASH [6] when operated in long bunchtrain mode of operation.

  • Open Access Logo Contribution to proceedings
    IPAC2012, 20.-25.05.2012, New Orleans, USA
    Proceedings of IPAC2012

Permalink: https://www.hzdr.de/publications/Publ-17157
Publ.-Id: 17157


Sorption of U(VI) and Np(V) onto diorite from Äspö HRL

Schmeide, K.; Gürtler, S.; Müller, K.; Steudtner, R.; Joseph, C.; Bok, F.; Brendler, V.

Sorption of the redox-sensitive actinides U and Np onto diorite obtained from Äspö Hard Rock Laboratory (HRL, Sweden) was studied by batch sorption experiments. The influence of various parameters, such as solid-to-liquid ratio (2 to 200 g/L), grain size (0.063 – 0.2 mm, 0.5 – 1 mm, 1 – 2 mm) and temperature (25 and 10°C), on the actinide sorption was studied under anoxic conditions (N2) applying a synthetic Äspö groundwater (pH 7.8, I = 0.178 M). The influence of grain size on actinide sorption was also investigated under aerobic conditions (pCO2 = 10−3.5 atm). Applying NaClO4 as background electrolyte, the actinide sorption onto diorite was studied as a function of ionic strength (I = 0.1 to 1 M, pH 7.8). Distribution coefficients, Kd values, were determined. Radionuclide speciation in solution was verified by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Furthermore, the sorption of U and Np onto diorite was also studied by in situ time-resolved attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy to characterize the sorbed species.

Keywords: Diorite; uranium; neptunium; sorption; speciation; TRLFS; ATR FT-IR spectroscopy

  • Lecture (Conference)
    1st Workshop of the Project "Crystalline rock retention processes" (CROCK), 22.-24.05.2012, Stockholm, Sweden
  • Poster
    1st Workshop of the Project "Crystalline rock retention processes" (CROCK), 22.-24.05.2012, Stockholm, Sweden
  • Contribution to proceedings
    1st Workshop of the Project "Crystalline rock retention processes" (CROCK), 22.-24.05.2012, Stockholm, Sweden
    1st Workshop Proceedings of the Collaborative Project “Crystalline Rock Retention Processes” (7th EC FP CP CROCK), KIT Scientific Reports 7629, Karlsruhe: KIT Scientific Publishing, 169-180 (2012)
  • Lecture (others)
    Status-Seminar 2012 "Nuclear Safety Research – From Reactors to Disposal", 11.-12.12.2012, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-17156
Publ.-Id: 17156


Laser proton accelerator for radiobiological studies

Zeil, K.; Beyreuther, E.; Karsch, L.; Kluge, T.; Laschinsky, L.; Kraft, S. D.; Oppelt, M.; Pawelke, J.; Richter, C.; Schürer, M.; Cowan, T.; Sauerbrey, R.; Schramm, U.

  • Poster
    Oncoray Retreat, 07.-08.03.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17155
Publ.-Id: 17155


Beam collimation with pulse power solenoids

Kroll, F.; Joost, M.; Burris-Mog, T.; Herrmanndörfer, T.; Kraft, S. D.; Sobiella, M.; Wustmann, B.; Zherlitsyn, S.; Cowan, T.; Schramm, U.

  • Poster
    Oncoray Retreat, 07.-08.03.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17154
Publ.-Id: 17154


Laser Proton Acceleration from Reduced Mass Targets

Zeil, K.; Metzkes, J.; Kraft, S.; Kluge, T.; Bussmann, M.; Schmidt, B.; Zier, M.; Schramm, U.; Cowan, T.; Sauerbrey, R.

We present recent studies on laser proton acceleration experiments using mass limited silicon targets. Small micro machined silicon foils with 2 µm thickness and 20x20 µm2 to 100x100µm2 size mounted on very tiny stalks were shot with ultra short laser pulses 30 fs of the new 150 TW DRACO Laser facility of the Research Centre Dresden-Rossendorf. The experiments were carried out using high contrast level 10-10. Proton spectra have been measured with magnetic spectrometers and radio chromic film stacks. The scaling of the maximum proton energy as function of the target size was investigated and strong influence of the stalk as well as the target edges was found.

  • Lecture (Conference)
    SPIE Optics and Optoelectronics, 18.-21.04.2011, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-17153
Publ.-Id: 17153


Fluid flow driven self-generation of magnetic fields in laboratory experiments

Giesecke, A.; Stefani, F.; Gerbeth, G.

Cosmic magnetic fields are ubiquitous phenomena that are intrinsically coupled to most astrophysical objects like planets, stars or galaxies. The origin of these fields involves the formation of electrical currents by means of a complex flow of a conducting fluid or plasma.This process, the so called dynamo effect, is necessarily three dimensional and non-linear which makes an analytical or numerical approach difficult.

Meanwhile, fluid flow driven generation of magnetic fields has also been obtained in laboratory experiments providing a complementary tool to astronomical observations or direct numerical simulations. However, whereas astrophysical dynamo action is comparably easy because of the large dimensions of the involved flows, its experimental realization requires considerable technical efforts. So far only three experiments have been able to demonstrate fluid flow driven self-excitation of magnetic fields.

I will briefly summarize the essential outcome of the seminal experiments conducted in Riga and in Karlsruhe which have demonstrated the principal possibility of the magnetic field generation process and its saturation. I will further discuss recent results of the French Von-Karman-Sodium dynamo that are still not completely understood, e.g. the dominance of the axisymmetric field or the exclusive occurrence of dynamo action when soft iron impellers are used to drive the flow.

Further progress in the experimental examination of dynamo action is expected from the future dynamo facility that is scheduled at the Helmholtz-Zentrum Dresden-Rossendorf. The DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN), which is presently in the design phase, will comprise a number of large scale liquid sodium experiments devoted to problems of geo- and astrophysical magnetohydrodynamics. A homogeneous dynamo, driven exclusively by precession, will represent the most ambitious compound of DRESDYN. Another experiment, a sodium filled Taylor-Couette cell, will allow the combined investigation of various versions of the magnetorotational instability and of the Tayler instability. For both experiments, recent results of preparatory studies are presented, and the scientific prospects for the final set-ups are delineated.

Keywords: dynamo

  • Lecture (Conference)
    Plasma Physics Symposium, 24.-25.05.2012, Bochum, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17152
Publ.-Id: 17152


Influence of the Lagrangian integral time scale estimation in the near wall region on particle deposition

Lecrivain, G.; Hampel, U.

In a high temperature pebble-bed reactor core where thousands of pebbles are amassed, the friction between the outer graphite layer of the fuel elements triggers the formation of carbonaceous dust. This dust is eventually conveyed by the cooling carrier phase and deposits in the primary circuit of the high temperature reactor. The numerical prediction of carbonaceous dust transport and deposition in turbulent flows is a key safety issue. Most particle tracking procedures make use of the Lagrangian integral time scale to reproduce the turbulent dispersion of the discrete phase. In the present Lagrangian particle tracking procedure, the effect of the Lagrangian integral time scale near the wall is thoroughly investigated. It is found that, in the linear sublayer, a value of the normalised wall normal component of the Lagrangian integral time scale lower that 4 delivers accurate particle deposition velocities. The value worked out here near the wall region is in accordance with Lagrangian integral time scales derived from recent Direct Numerical Simulations.

Keywords: particle deposition; turbulent dispersion; CFD

  • Journal of Fluids Engineering - Transactions of the ASME 134(2012)7, 074502
    DOI: 10.1115/1.4006912

Permalink: https://www.hzdr.de/publications/Publ-17150
Publ.-Id: 17150


Cm(III) and Eu(III) speciation in human body fluids and cell culture media studied by luminescence spectroscopy

Heller, A.; Barkleit, A.; Sachs, S.; Bernhard, G.

The speciation of curium and europium in urine, saliva and FaDu cell culture medium is studied with time-resolved laser-induced fluorescence spectroscopy.
The complexation study of Cm(III)/Eu(III) with inorganic and organic model substances like carbonate, phosphate, citrate and various proteins which is crucial for species identification in biofluids is presented.

Keywords: curium; europium; urine; saliva; cell culture medium; TRLFS

  • Invited lecture (Conferences)
    4th Speciation Seminar, 29.-31.05.2012, Montpellier, France

Permalink: https://www.hzdr.de/publications/Publ-17149
Publ.-Id: 17149


Autonome Sensorpartikel zur räumlichen Parametererfassung in großskaligen Behältern

Reinecke, S.; Pöpping, U.; Hampel, U.

Zur Langzeiterfassung räumlich verteilter Parameter in Prozessbehältern wurde das Konzept autonomer Sensorpartikel entwickelt und getestet. Die Sensorpartikel sind auftriebsneutral und bewegen sich frei mit der vorherrschenden Strömung im Prozess. Die integrierte Messelektronik erfasst die Signale der internen Messfühler für die Temperatur, die Eintauchtiefe und die Beschleunigung in einem autonomen und energieeffizienten Messregime. Die Validierung des Messsystems erfolgte unter realen Strömungsbedingungen in einem Versuchsfermenter. Die aufgenommenen Messdaten und die daraus extrahierten Prozesskenndaten charakterisieren den Zustand des Prozesses und die vorherrschenden Strömungsbedingungen.

  • Contribution to proceedings
    16. GMA/ITG Fachtagung Sensoren und Messsysteme 2012, 22.-23.05.2012, Nürnberg, Deutschland
    Sensoren und Messsysteme 2012 - Vorträge der 16. GMA/ITG Fachtagung, 978-3-9813484-0-8, 513-521
  • Lecture (Conference)
    16. GMA/ITG Fachtagung Sensoren und Messsysteme 2012, 22.-23.05.2012, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17148
Publ.-Id: 17148


Modeling of SFR cores with Serpent-DYN3D codes sequence

Fridman, E.; Shwageraus, E.

DYN3D reactor dynamics nodal diffusion code was originally developed for the analysis of Light Water Reactors. In this paper, we demonstrate feasibility of using DYN3D for modeling of fast spectrum reactors. Homogenized cross sections data library was generated using continuous energy Monte-Carlo code Serpent which provides significant modeling flexibility compared with traditional deterministic lattice transport codes and tolerable execution time. A representative sodium cooled fast reactor core was modeled with Serpent-DYN3D code sequence and the results were compared with those produced by ERANOS code and with 3D full core Monte Carlo solution. Very good agreement between the codes was observed for the core integral parameters and power distribution suggesting that DYN3D code with cross section library generated using Serpent can be reliably used for the analysis of fast reactors.

Keywords: Serpent; Monte Carlo; lattice physics; DYN3D; few-group cross-section generation; sodium cooled fast reactor

Permalink: https://www.hzdr.de/publications/Publ-17147
Publ.-Id: 17147


Modification of ZnO:Al properties: post-deposition millisecond thermal processing vs direct growth at elevated substrate temperature

Vinnichenko, M.; Hauschild, D.; Cornelius, S.; Krause, M.; Gago, R.; Mücklich, A.; Lissotschenko, V.; Kolitsch, A.

ZnO:Al (AZO) is a promising cost-efficient transparent conducting material for a number of applications. Thermal processing at millisecond time scale (very rapid thermal processing, vRTP) is an attractive approach of AZO film properties improvement. Present study focuses on systematic comparison of the properties of the films processed by vRTP and directly grown at various substrate temperatures. The AZO films were deposited both by reactive pulsed and non-reactive DC magnetron sputtering. The vRTP was performed using innovative low-cost high power diode laser arrays with microoptically designed line-shaped beam profiles (dwell time of 1 ms). Only the films grown without substrate heating were subjected to the vRTP. Even at air ambience, the optimized laser processing of the AZO films results in a decrease of the film electrical resistivity from (1-2)x10^-3 to less than 5x10^-4 Ohm cm. This is accompanied by a substantial, in some cases almost two-fold, increase of the free electron mobility and density, and increase of the film transmittance in the visible. According to TEM, ellipsometry, Raman spectroscopy and XANES, annealing of intra-grain oxygen-related point defects during vRTP has a main effect on the film electrical properties. Using deposition at elevated temperature, the AZO films with comparable electrical and optical properties were achieved only at Ts≥250°C.

Keywords: transparent conductive oxides; ZnO:Al; very rapid thermal processing

  • Invited lecture (Conferences)
    10th International Symposium on Ceramic Materials and Components for Energy and Environmental Applications (10th CMCEE), 21.-23.05.2012, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-17146
Publ.-Id: 17146


Plasmonic nano-Ag layers in TCO and Si nanosponge for photovoltaic applications

Vinnichenko, M.; Liedke, B.; Heinig, K.-H.; Gulseren, O.; Friedrich, D.; Mücklich, A.; Schmidt, B.; Akguc, G. B.; Aydinli, A.

Ag nanoparticles (NPs) have the potential of increasing efficiency of thin film solar cells substantially due to plasmonic effects. Here, we consider two different approaches of Ag NPs embedding into: (i) transparent conductive oxide (TCO) at the rear side of thin-film PV cells to induce plasmonic scattering of red light at high angles (in-plane direction) in order to improve the light trapping in the absorber layer; and (ii) absorber layer to increase carrier generation due to plasmonic field enhancement.
For the approach (i), a thin Ag layer is sandwiched between two ZnO:Al films with all films grown by magnetron sputter deposition. Subsequently, by a thermal treatment or using high growth temperatures this Ag film is transformed into an Ag NP layer via spinodal dewetting. The formation of Ag NPs was investigated experimentally and by atomistic simulations. The electrical and optical properties of such composites were also studied.
For the approach (ii) Ag layer can be sandwiched between SiO layers grown by PVD and then thermally treated to form novel absorber material consisting of Si nanowire network in SiO2 and Ag NPs. Large-scale atomistic simulations predict formation of Ag/Si core-shell NPs isolated by SiO2. This prevents direct electrical contact of Ag NPs with percolated Si network, thus avoiding charge carriers losses. The experimental prove of this prediction is in progress.

Keywords: Transparent conductive oxides; plasmonic effects

  • Poster
    E-MRS Spring Meeting, 14.-18.05.2012, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-17145
Publ.-Id: 17145


Mechanisms of electrical and optical properties modification of ZnO:Al films induced by very rapid thermal processing

Vinnichenko, M.; Hauschild, D.; Cornelius, S.; Krause, M.; Gago, R.; Mücklich, A.; Neidhardt, J.; Lissotschenko, V.; Kolitsch, A.

Thermal processing at millisecond range (very rapid thermal processing, vRTP) is an attractive approach of ZnO:Al film properties improvement compared to RTP or time-consuming isothermal annealing. This is of importance for development of cost-efficient transparent electrodes for thin film solar cells. The present study elucidates the effects of thermal processing on the film optical and electrical properties comparing vRTP treatment at ambient atmosphere using a laser source (~1 ms dwell time) with isothermal annealing in vacuum (1 hour, Ta≤550 °C). The films were grown by reactive pulsed magnetron sputtering (MS) at lab scale and non-reactive MS using an industrial in-line system. The optimized laser processing and the isothermal annealing of the films grown at low temperatures (RT-100 °C) result in an increase of their transmittance in the visible, decrease of electrical resistivity from (1-2)x10^-3 to less than 5x10^-4 Ohm cm, substantial increase of free electron mobility, µe, and density, Ne. Laser annealing of the films grown under optimized conditions at 350 °C does not improve their properties, while isothermal annealing leads to an increase of µe values above 50 cm2V-1s-1. According to TEM, ellipsometry, Raman spectroscopy and XANES, annealing of intra-grain oxygen-related point defects during vRTP has a main effect on the film electrical properties, while during isothermal annealing additional improvement of crystallinity needs to be taken into account.

Keywords: transparent conductive oxides; ZnO:Al; high-power diode laser annealing

  • Lecture (Conference)
    E-MRS Spring Meeting, 14.-18.05.2012, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-17144
Publ.-Id: 17144


Terahertz spectroscopy of semiconductor nanostructures with the free-electron laser

Helm, M.

Free electron lasers (FEL) can deliver high-intensity narrow-band radiation in otherwise not easily accessible spectral ranges, such as the THz range.
After briefly introducing the FEL at HZDR, I will discuss a quantum optical experiment, where we use the FEL to drive the 1s-2p intra-excitonic transition in semiconductor quantum wells and observe the so-called Autler-Townes splitting, a manifestation of electronic states dressed by the radiation field [1]. Our results indicate that we enter a regime well beyond the rotating-wave and two-level approximations. As a second example I will discuss pump-probe experiments on multilayer graphene over a wide range of photon energies (10-250 meV), hereby unveiling the relevant electronic relaxation mechanisms [2]. Remarkably we observe a sign change of the probe signal, i.e. a crossover from induced bleaching to induced absorption, which is related to the interplay between inter- and intraband absorption.

[1] M. Wagner, H. Schneider, D. Stehr, S. Winnerl, A. M. Andrews, S. Schartner, G. Strasser, M. Helm: „Observation of the intra-exciton Autler-Townes effect in GaAs/AlGaAs semiconductor quantum wells”, Phys. Rev. Lett. 105, 167401 (2010)

[2] S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W. A. de Heer, H. Schneider, M. Helm: "Carrier relaxation in epitaxial graphene photoexcited near the Dirac point", Phys. Rev. Lett. 107, 237401 (2011)

Keywords: free-electron laser; semiconductor nanostructures; terahertz; graphene

  • Invited lecture (Conferences)
    Physikkolloquium TU Chemnitz, 23.05.2012, Chemnitz, Deutschland
  • Invited lecture (Conferences)
    Physikkolloquium Universität Konstanz, 26.06.2012, Konstanz, Deutschland
  • Invited lecture (Conferences)
    Physikkolloquium Universität Paderborn, 12.07.2012, Paderborn, Deutschland
  • Lecture (others)
    Seminarvortrag Southeastern University, Nanjing, China, 18.09.2012, Nanjing, China

Permalink: https://www.hzdr.de/publications/Publ-17143
Publ.-Id: 17143


Novel 7α-alkoxy-17α-(4’-halophenylethynyl)estradiols as potential SPECT/PET imaging agents for estrogen receptor expressing tumors: synthesis and binding affinity evaluation

Neto, C.; Oliveira, M. C.; Gano Fernanda Marques, M. L.; Yasuda, T.; Thiemann, T.; Kniess, T.; Santos, I.

To develop potential radiolabelled probes for SPECT/PET imaging estrogen receptor (ER) positive tumors, we have synthesized and characterized a series of novel 7α-alkoxy-17α-(4-iodophenylethynyl)estra-1,3,5(10)-triene-3,17β-diols and 7α-alkoxy-17α-(4-fluorophenylethynyl)estra-1,3,5(10)-triene-3,17β-diols.
The fluoro-substituted compounds showed a higher ER binding affinity than the corresponding iodo-compounds, where 7α-methoxy- and 17α-(4-fluorophenylethynyl)estra-1,3,5(10)-triene-3,17β-diol showed the highest ER binding affinities (RBA=80.9 and 78.9%) among the halophenylethynyl compounds studied and should be further explored as potential PET biomarkers for imaging of ER expressing tumors.

Permalink: https://www.hzdr.de/publications/Publ-17142
Publ.-Id: 17142


A 2m x 0.5m prototype of a MRPC-based neutron detector with steel converter plates

Röder, M.; Aumann, T.; Bemmerer, D.; Boretzky, K.; Caesar, C.; Cowan, T. E.; Hehner, J.; Heil, M.; Elekes, Z.; Kempe, M.; Maroussov, V.; Reinhardt, T. P.; Simon, H.; Sobiella, M.; Stach, D.; Wagner, A.; Wüstenfeld, J.; Yakorev, D.; Zilges, A.; Zuber, K.; for the R3B Collaboration

A 2m long prototype detector for the detection of neutrons in an energy range from 200MeV to 1 GeV has been successfully realized. The working principle is based on steel converter plates followed by an MRPC structure to detect charged particles produced by hadronic interactions. In order to study time resolution and efficiency, a 2m x 0.5m large module has been built which comprises a 2 x 2 gap MRPC structure. An efficiency larger than 90% and a time resolution better than 100 ps have been measured for minimum ionizing electrons. This experiment has been done using the one-electron-per-bunch mode of the superconducting electron linear accelerator ELBE, Dresden. Another test has been done using 175MeV quasi-monochromatic neutrons at TSL in Uppsala. A test using tagged high-energy neutrons is scheduled at GSI. Extensive Monte Carlo simulations have been carried out, both for the electron-beam tests and for the final application as a neutron detector. The present approach offers a cost-effective way for the time-of-flight detection of high energy neutrons.

Keywords: Detector - MRPC; neutron beam; electron beam; minimum ionizing electrons; Monte Carlo simulations

  • Lecture (Conference)
    XI workshop on Resistive Plate Chambers and Related Detectors (RPC 2012), 05.-10.02.2012, Frascati (Rom), Italien
  • Open Access Logo Proceedings of Science RPC(2012)

Permalink: https://www.hzdr.de/publications/Publ-17141
Publ.-Id: 17141


Three natural minerals - sanidine, pyrite and columbite - as potential geologic reference materials. Characterization of chemical homogeneity at a micrometer scale

Michalak, P. P.; Renno, A. D.; Munnik, F.; Radtke, M.; Buzanich, G.; Reinholz, U.; Merchel, S.

A supply risk assessment of strategic high-technology metals requires a thorough quality assurance of their concentration in ores. Because such metals are usually unevenly distributed at a micrometer scale within natural ore-minerals matrices, spatially-resolved methods must be employed in geometallurgic investigations. Unfortunately, obtaining reliable data with non-absolute micro-analytical methods requires the use of reference materials
(RMs) that fulfill the matrix-match criterion. While using natural minerals with optimum chemical composition as reference materials seems to satisfy the matrix criterion, assuring their chemical homogeneity at the sub-µg/g sampling masses usually fails. A solution is to produce synthetic minerals, doped with high-technology metals at trace concentrations, evenly distributed in homogenous chemically-optimal matrices.
Prior to the synthesis, three natural minerals - sanidine, pyrite and columbite - have been tested for lateral chemical and structural homogeneity. The assessment involved both microscopic (optical) and spectroscopic methods. The samples have been visually examined with a reflected light microscope and electron microscope (Back Scattered Emission imaging) exhibiting no optical heterogeneities. The chemical composition has been analyzed with three methods based on X-ray detection: EPMA (Electron Probe Micro Analysis), PIXE (Particle Induced X-ray Emission) and Sy-XRF (Synchrotron radiation-induced X-ray Fluorescence). EPMA analyses were carried out at the TU Bergakademie Freiberg using a wavelength dispersive spectrometer (WDS) and an accelerating voltage of 20 keV and a beam size of 2 µm2. PIXE data were obtained using a 3 MeV proton beam of about 5x5 µm2 from a 3 MV tandem accelerator at the HZDR in Dresden. Sy-XRF measurements were performed at the hard X-ray beamline “BAMline” at the BESSY synchrotron facility in Berlin. Samples were exposed in atmosphere to monochromatic X-rays of 20 keV focused with a compound refractive lens to 3x3 µm2.
Petrographically-sensible homogeneity testing procedure has been implemented into statistical analysis of the results accounting for both random and systematic heterogeneity patterns such as nugget and island type as well as periodic wave-type heterogeneities.
Quantitative (EPMA, PIXE) and qualitative (Sy-XRF) elemental spatial distribution maps have been obtained for major, minor and trace elements for each scan. Several trace elements were detected in each of the matrices: Ga, Ge, Rb, Sr, Ba in sanidine; Ni, Cu, As in pyrite and Zr, Sc, Y, W in columbite. All of them showed irregular distribution patterns, proving that selected mineral specimens are not suitable candidates for reference materials.
The proposed sequence of testes including microscopic and spectroscopic microanalytical techniques and standardized statistical procedures turn out to be adequate in quality assurance of minerals and will be used as a template in examining our synthetic material.

Keywords: EPMA; PIXE; Sy-XRF; reference materials

  • Poster
    European Mineralogical Conference 2012, 02.-06.09.2012, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17140
Publ.-Id: 17140


Interaction between europium and calcite: macroscopic and spectroscopic studies

Sabău, A.; Marmier, N.; Jordan, N.; Lomenech, C.; Barkleit, A.; Toulhoat, N.; Pipon, Y.; Moncoffre, N.; Brendler, V.; Giffaut, E.

Interactions between cations and natural or synthetic calcite may include incorporation processes, resulting in the irreversibility of some sorption reactions. Understanding and quantification of poorly to non reversible trapping mechanisms can be considered as a significant improvement in the description of a geological barrier or a backfill material performance in the safety assessment. To investigate these irreversible processes, we have decided to work on the Eu-CO2-NaCl-CaCO3 system at pH 8.3, buffered by calcite under air and corresponding to the typical pH range of natural interstitial groundwaters. Europium was chosen as analogue for trivalent actinides and due to its fluorescence properties enabling its study by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Our study combines macroscopic batch investigations and the use of spectroscopic tools to comprehensively characterize this system.
At first, a material appropriate for sorption experiments had to be selected, based on characterization studies. From a variety of sources, we focused on a calcite from SOLVAY (SOCAL U1-R) with a particle size of 0.2 µm for TRLFS investigations, mainly due to its large BET specific surface area (18.4 m2/g). We also used a calcite from OMYA (BL 200), with a bigger particle size (56 µm) and a lower specific surface area (0.66 m2/g) for Rutherford Backscattering Spectrometry (RBS) measurements, due to the specific requirements of this technique. Purity of the calcite samples and absence of polymorphic CaCO3 compounds (i.e. vaterite and aragonite) were confirmed by XRD, DRIFT or SEM.
The second step of the work was to investigate the irreversible Eu(III) uptake mechanisms onto calcite. Batch experiments, done under atmospheric conditions (pCO2 = 10−3.5), were performed under different element concentration (10−5, 10−4 and 10−3 M) and contact time (4 hours, 1 day, 1 week and 1 month), which are assumed to be the most important parameters controlling the transition between adsorption and incorporation into the solid. In addition, this allowed to monitor the potential changes in mechanisms with time. The concentrations of Eu and Ca left in the supernatant were determined by ICP-MS and ICP-OES, respectively.
Europium species formed in solution and at the solid/solution interface were identified by TRLFS. Reference blank (Eu3+ in solution and Eu3+ precipitated) spectra were compared with the sorbed samples. When elements such as europium are sorbed onto a mineral surface by inner-sphere complexation, some of the H2O molecules in the first coordination sphere are displaced. Such changes should impact the fluorescence lifetime of Eu species.
The spectrum presented in Fig. 1 corresponds to Eu-reacted calcite after a contact time of 1 month and an initial concentration of Eu of 10-4 M. Europium was found to be completely sorbed onto calcite, whose dissolution was negligible. Two lifetimes were identified. The lower value, so far not reported in the literature, can thus not unambiguously be attributed to a specific Eu species. However, the higher second lifetime is correlated with the complete loss of the europium hydration sphere, suggesting either a surface precipitate or an incorporation.
RBS measurements (Fig. 2) were carried out using the 4 MV Van De Graaff accelerator facility of IPNL with a 4 MeV incident alpha beam. They were performed at the same Eu concentration as the TRLFS results (Fig. 1), in order to obtain a high resolution signal. RBS results confirmed those obtained by TRLFS, by showing an accumulation of europium onto the calcite surface.
It can be concluded that TRLFS and RBS are appropriate and complementary techniques to study the Eu-CO2-NaCl-CaCO3 system. The results obtained so far indicate that there is either a surface precipitate following a first sorption step or that incorporation into the bulk crystal lattice already started. Both processes may occur simultaneously, further experiments shall reveal this.

Keywords: europium; calcite; TRLFS; RBS; sorption; incorporation

  • Poster
    Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, 22.-25.10.2012, Montpellier, France

Permalink: https://www.hzdr.de/publications/Publ-17139
Publ.-Id: 17139


Magnetic shielding of implanted magnetic scaffolds and fixators

Uhlarz, M.

es hat kein Abstract vorgelegen

  • Lecture (Conference)
    MAGISTER Month 36 Review Meeting, 16.-18.01.2012, Rom, Italy

Permalink: https://www.hzdr.de/publications/Publ-17138
Publ.-Id: 17138


Magnetic characterization of magnetosome growth in mesenchymial stem cells

Uhlarz, M.

es hat kein Abstract vorgelegen

  • Lecture (Conference)
    MAGISTER Month 36 Review Meeting, 16.-18.01.2012, Rom, Italy

Permalink: https://www.hzdr.de/publications/Publ-17137
Publ.-Id: 17137


Effects of sterilizing gamma-ray irradiation on Fe-hydroxyapatite paste

Uhlarz, M.

es hat kein Abstract vorgelegen

  • Lecture (Conference)
    MAGISTER Month 36 Review Meeting, 16.-18.01.2012, Rom, Italy

Permalink: https://www.hzdr.de/publications/Publ-17136
Publ.-Id: 17136


Magnetic characterization of scaffold materials, simulators and powders

Uhlarz, M.

es hat kein Abstract vorgelegen

  • Lecture (Conference)
    MAGISTER Month 36 Review Meeting, 16.-18.01.2012, Rom, Italy

Permalink: https://www.hzdr.de/publications/Publ-17135
Publ.-Id: 17135


Thin film PV cell with Ag nanoparticle layers in TCO and Si nanosponge absorber

Liedke, B.; Heinig, K.-H.; Gulseren, O.; Akguc, G. B.; Vinnichenko, M.

The plasmonic action of Ag nanoparticles has the potential to increase the efficiency of thin film PV cells substantially. Here, two different actions will be considered: (i) Ag nanoparticles (NPs) embedded in the Transparent Conductive Oxide (TCO) at the rear side of thin-film PV cells can induce plasmonic scattering of red light, which increases the light way and therefore the absorption in the absorber layer. (ii) Ag NPs embedded in the absorber layer increases carrier generation due to plasmonic light field enhancement.
For the plasmonic action (i), a thin Ag layer is sandwiched between ZnO:Al by sputter deposition. Subsequently, by a thermal treatment this Ag layer is decomposed via spinodal dewetting into an Ag NP layer. Structural, electrical and optical properties are investigated theoretically, by atomistic simulation and FDTD and boundary element calculations, and experimentally.
For the plasmonic action (ii) it has to be avoided that Ag NPs in the absorber layer become charge carrier killer. Usually this is impossible, but in our novel absorber consisting of a Si nanowire network (nanosponge) in SiO2, the Ag NPs can be located in SiO2 without contact to the electrically percolated Si network. Based on large-scale atomistic simulations it is predicted that such a nanocomposite can be synthesized by PVD deposition of SiO with a sandwiched thin Ag layer. It will be shown that subsequent thermal treatment results in nanosponge with Ag/Si core-shell NPs in SiO2.

Keywords: TCO; AZO; plasmonics; Ag nanoparticles; ZnO; kinetic Monte-Carlo; FDTD; boundary element method; light harvesting

  • Lecture (Conference)
    E-MRS 2012 Spring Meeting, 14.-18.05.2012, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-17134
Publ.-Id: 17134


EFTEM studies of Si nanowire networks in SiO2 for thin film PV cells

Liedke, B.; Mücklich, A.; Heinig, K.-H.; Schmidt, B.; Friedrich, D.; Keles, U.; Bulutay, C.

Si based nanostructures became in the last years a promising material for the PV cells. The quantum confinement effect of Si nanostructures allows for band gap engineering by size manipulation which can be used for optimization sun light absorption.
Here, we consider SiOx layers deposited by magnetron sputtering. By subsequent rapid thermal processing, SiOx decays by spinodal decomposition into a network of Si nanowires (NWs) in SiO2.
To get images of the morphology of Si NWs in SiO2 it is not sufficient to use mass contrast or lattice plane imaging. The Si and SiO2 phases can only be distinguished by energy filtering of the transmitted electrons (EFTEM). Here, the relative energy shifts of the plasmonic valence band resonances of Si and SiO2 are used. HR-EFTEM techniques are applied to study morphology and crystallinity of the Si NW networks fabricated from different metastable SiOx. To facilitate understanding of the TEM images, details of decomposition are studied using kinetic Monte-Carlo (KMC) simulations. For the EFTEM images, density-density correlations are calculated to determine the structure size of NW network, which are then compared with the 3D morphologies provided by KMC. Combining EFTEM with KMC allows us to predict and control the average size of the NWs.
Former studies and our electronic structure calculations provide a guideline for band gap optimization of Si NW networks, thus paving the way to band gap engineering via control of the mean NW diameter.

Keywords: kinetic Monte-Carlo; TEM; EFTEM; Silicon nanowires; nanosponge; nanocrystals

  • Lecture (Conference)
    E-MRS 2012 Spring Meeting, 14.-18.05.2012, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-17133
Publ.-Id: 17133


Si-nanosponge embedded in SiO2 as a new absorber material for photovoltaics

Liedke, B.; Heinig, K.-H.; Schmidt, B.; Friedrich, D.; Mücklich, A.; Kelling, J.; Hauschild, D.

Silicon based nanostructures became within the last years most promising material for the PV market. Quantum confinement effect of nanostructured silicon allows for band gap engineering just by size manipulation to absorb the light in more efficient way.
Here, we consider SiOx layers fabricated by magnetron co-sputter deposition, which after thermal treatment decompose into a network of Si nanowires embedded in SiO2. The thermally activated spinodal decomposition is performed by rapid thermal processing within a few seconds and by very rapid thermal processing within several ms using diode laser. The morphology and crystallinity of the Si-nanosponge was measured by energy filtered TEM and Raman, respectively. The details of decomposition are studied using the atomistic kinetic Monte-Carlo (KMC) simulations at different concentrations defined by the x parameter. The spatiotemporal temperature profiles T(x, t) of the scanned laser has been calculated as a function of thickness and time by the heat transport equation. The obtained profiles are used in the KMC. The combined theoretical and experimental investigations support the band gap engineering of the Si-nanosponge absorber via a control of the quantum confinement.

Keywords: Silicon nanostructures; Nanocrystals; TEM; EFTEM; kinetic Monte-Carlo; RTP; vRTP; Raman; nanosponge

  • Lecture (Conference)
    76. Jahrestagung der DPG und DPG-Frühjahrstagung, 25.-30.03.2012, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17132
Publ.-Id: 17132


Experiences with Positron Lifetime Spectroscopy using a multi-detector setup

Butterling, M.; Anwand, W.; Hartmann, A.; Wagner, A.; Haeberle, J.; Jungmann, M.; Krause-Rehberg, R.; Krille, A.; Muchow, M.

First experiments and gained knowledge using and improving a multi-detector setup for Positron Lifetime Spectroscopy are presented.

Keywords: Positron Lifetime Spectroscopy; Positron Lifetime; Multi-Detector Setup

  • Lecture (Conference)
    Treffen deutscher Positronengruppen, 28.02.-01.03.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17131
Publ.-Id: 17131


Endlagerung radioaktiver Abfälle: Wie tief muss man graben für eine Million Jahre Sicherheit?

Müller, K.

Der Vortrag gibt eine Übersicht über die in Deutschland anfallenden radioaktiven Abfälle. Desweiteren werden die Anforderungen an die sichere Verwahrung dieser Abfälle, hinsichtlich hoher Temperaturen, Wirtsgesteinseigenschaften und die sehr langen Lagerungszeiträume beleuchtet.

  • Lecture (others)
    Tag des offenen Labors 2012, 12.05.2012, Dresden, Deutschland
  • Lecture (others)
    Lange Nacht der Wissenschaften in Dresden, 06.07.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17130
Publ.-Id: 17130


Redox behavior of Tc(VII)/Tc(IV) under various reducing conditions in 0.1 M NaCl solutions

Kobayashi, T.; Scheinost, A. C.; Fellhauer, D.; Gaona, X.; Altmaier, M.

Redox behaviour of Tc(VII)/Tc(IV) was investigated under inert Ar atmosphere in 0.1 M NaCl solutions containing different reducing agents in the pH range 2 to 13 at 22ºC. Under certain conditions, the 1•10−5 mol/dm3 (M) initial TcO4– was reduced to form a sparingly soluble Tc(IV) oxide solid phase. The results can be systematized according to Eh-pH conditions. It is found that an experimental borderline for the reduction of Tc(VII) to Tc(IV), TcO4− + 3e− + 4H+  TcO2∙xH2O(coll, hyd) + (2−x)H2O is established, which is independent of the reducing chemical system. This experimental borderline is about 100 mV lower than the equilibrium line calculated from the reported standard redox potential of TcO2∙1.6H2O(s). This behaviour can be explained by the existence of more soluble solid phase modifications like small Tc(IV) oxide particles (TcO2・xH2O(coll,hyd)). The reaction kinetics correlate to the redox potentials measured in solution. Slow reduction of Tc(VII) to Tc(IV) was observed when the redox potential in the system was near the reduction borderline. Fast reduction was observed in the systems far from the borderline or containing Fe(II) solids, suggesting a specific surface mediated effect in the reduction process. EXAFS analysis on two magnetite samples indicate reduced Tc(IV) species which do not remain adsorbed at the reactive magnetite surface, but are incorporated in its structure.

Keywords: redox; Tc; EXAFS; XANES; magnetite

Permalink: https://www.hzdr.de/publications/Publ-17129
Publ.-Id: 17129


Latest results on fs-synchronization and RF at ELBE

Kuntzsch, M.

Presentation of latest results of femtosecond Synchronization System, including commissioning of first prototype link stabilizer. Additional information on preliminary test of new ELBE master oscillator unit.

Keywords: Synchronization ELBE RF Jitter

  • Lecture (others)
    Thomas Jefferson National Accelerator Facility Free Electron Laser Colloquium, 23.04.2012, Newport News, USA

Permalink: https://www.hzdr.de/publications/Publ-17128
Publ.-Id: 17128


Nitrogen interstitial diffusion induced decomposition in AISI 304L austenitic stainless steel

Martinavicius, A.; Abrasonis, G.; Scheinost, A. C.; Danoix, R.; Danoix, F.; Stinville, J. C.; Talut, G.; Templier, C.; Liedke, M. O.; Gemming, S.; Möller, W.

The nature of the near-surface γN phase produced by low-temperature (∼400 °C) plasma-assisted nitriding of an austenitic stainless steel 304L is studied. A combination of global probes (X-ray diffraction, nuclear reaction analysis, glow discharge optical emission spectroscopy) and local probes (field ion microscopy, conversion electron Mössbauer, X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopies) is employed to reveal the morphology, phase structure, atomic ordering and chemical state of the obtained γN phase. The results consistently reveal the heterogeneous nature of the nitrided layer consisting of nanometric CrN precipitates embedded in a Fe4N-like matrix. The size of the precipitates is found to be larger at the surface than at the nitrided layer–steel interface. The precipitates have irregular, sphere-like shapes. Moreover, X-ray spectroscopic investigation revealed three different intermetallic distances and different chemical environments for Fe, Cr and Ni, accompanied by a large static disorder. These findings suggest that the presence of the interstitial N destabilizes the homogeneous element distribution in 304L even at such low temperatures. This leads to the segregation into Cr-rich zones that are coherent with the Fe4N matrix. Possible atomistic decomposition mechanisms are discussed. Based on the heterogeneous nature of the γN phase revealed in 304L, an alternative view of its remarkable combination of properties such as large hardness, induced ferromagnetism and preserved corrosion resistance is considered.

Keywords: Stainless steel; Surface alloying; Interstitial diffusion; Decomposition; Precipitation

Permalink: https://www.hzdr.de/publications/Publ-17127
Publ.-Id: 17127


Alteration of magnetic anisotropy of Pt/Co/Pt trilayers by FIB irradiation

Mazalski, P.; Dobrogowski, W.; Sveklo, I.; Maziewski, A.; Fritzsche, M.; Liedke, M. O.; Fassbender, J.; Baczewski, L. T.; Wawro, A.

Investigation of the magnetic thin film structures with the out-of-plane magnetization are important for both fundamental research and applications. In nanostructures with decreasing magnetic film thickness an out-of-plane alignment of magnetization is frequently observed due to increasing contribution of surface anisotropy. It has been shown that ion beam irradiation modifies magnetic properties of such structures [1, 2]. With increasing irradiation dose D of such films the strength of perpendicular anisotropy is suppressed, magnetization rotates towards in-plane alignment or ferromagnetic ordering is converted to the superparamagnetic state. Very recently an oscillatory behaviour of magnetic anisotropy between the in-plane and out-of-plane states driven by an increasing dose of 30 keV Ga+ ion homogenous irradiation, has been observed in the molecular beam epitaxy (MBE) deposited Pt/(Co 3.3 nm)/Pt films [3].
The aim of this work is investigation of local modifications of magnetic properties in MBE grown Mo/Pt(20nm)/(Co3.3nm)/Pt(5nm) films by a focused ion beam (FIB). In the studied as deposited structure magnetization was aligned in the film plane. Numerous spots of the sample (squares 100x100μm² or 50x50μm²) have been locally irradiated with Ga+ ions with energy of 30 keV and different doses D ranging between 2•10^12 and 1•10^16 ions/cm². FIB irradiated spots were probed using polar/longitudinal Kerr effect magnetometry (sensitive to perpendicular/longitudinal magnetization component) and atomic/magnetic force microscopy techniques. Creation of the two out-of-plane magnetization branches upon increasing FIB irradiation dose D was observed, similarly to the effect reported for homogenous irradiation [3].
Presented results seem to be promising for new method for magnetic nanostructure patterning.

[1] C. Chappert et al., Science 280, 1919 (1998).
[2] J. Fassbender et al., J. Magn. Magn. Mat. 320, 579 (2008).
[3] A. Maziewski et al., Phys. Rev. B 85, 054427 (2012).

  • Poster
    Joint European Magnetic Symposia (JEMS 2012), 09.-14.09.2012, Parma, Italien

Permalink: https://www.hzdr.de/publications/Publ-17126
Publ.-Id: 17126


Application of positron beams to the investigation of memristive materials and diluted magnetic semiconductors

Potzger, K.; Liedke, M.

After a general introduction to the field of resistive switching and spin electronics and the role of defects therein, recent investigations on the above mentioned topics including positron beams are reviewed. An ongoing project at the Helmholtz Centre Dresden-Rossendorf to further extend such investigations is briefly outlined and expected benefits are mentioned.

Keywords: Resistive switching; memristive materials; diluted magnetic semiconductors; positrons

  • Book chapter
    B.N. Ganguly, G. Brauer: Near-Surfaces Depth Profiling of Solids by Mono-Energetic Positrons, Switzerland: Trans Tech Publishers, 2012, 978-3-03785-524-9, 235-251
    DOI: 10.4028/www.scientific.net/DDF.331.235

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-17125
Publ.-Id: 17125


Experiments with strong far-infrared radiation at the free-electron laser

Schneider, H.

There is no abstract.

  • Lecture (others)
    Kolloquium FB Physik, Universität Marburg, 14.05.2012, Marburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17124
Publ.-Id: 17124


High-power laser development projects for laser particle acceleration at HZDR

Zeil, K.; Baumann, M.; Beyreuther, E.; Bock, S.; Burris-Mog, T.; Cowan, T. E.; Enghardt, W.; Helbig, U.; Karsch, L.; Kraft, S. D.; Laschinsky, L.; Loeser, M.; Metzkes, J.; Naumburger, D.; Oppelt, M.; Pawelke, J.; Richter, C.; Roeser, F.; Sauerbrey, R.; Schürer, M.; Schramm, U.; Siebold, M.

Recent developments in the field of laser particle acceleration enable potential applications as, e.g., radiotherapy with laser driven proton beams. Laser driven proton therapy, not only requires sufficiently high proton energies but also a reasonable repetition rate for appropriate control of the dose delivery. In Dresden, this ambitious vision is addressed by close collaborative work at OncoRay (represented by Technical University Dresden and Helmhotz-Zentrum Dresden-Rossendorf (HZDR)) combining expertise in laser plasma physics, accelerator physics, and medicine. A dedicated research building later housing both, a laser driven proton beam delivery system and a conventional proton therapy accelerator for direct comparison in clinical trials is presently under construction.
For the development of a medical high intensity laser prototype to be installed at OncoRay we focus on two major projects in parallel. The first project uses a commercialized Ti:Sapphire based laser concept providing ultra short pulses of tens of femtoseconds at a repetition rate of 10 Hz. With the 150 TW Draco laser the proton acceleration process was investigated in the last three years [1], and a long-term stable and reliable mode of operation was established which has enabled first in vitro cell irradiation studies [2]. The laser system is presently upgraded by an additional amplifier stage and new front end components finally providing high contrast pulses of >500 TW on target at 1 Hz pulse repetition rate. By use of the increased pulse energy and the multiple beam option the proton energy scaling will be investigated and the radiobiological program will be extended to the irradiation of tumors in animals.
Complementary to the ultra short pulse laser approach, the direct diode pumped solid state laser PENELOPE is under development. The status of this energetically more efficient technology providing longer pulse durations at comparable beam power and therefore favoring potentially higher proton acceleration performance than ultra short pulses will be presented.

[1] Zeil, K. et al. New J Phys, 12, 045015, 2010.
[2] Kraft, S. et al. New J Phys 12, 085003 (2010).

  • Invited lecture (Conferences)
    Advanced Accelerator Concepts Workshop, 13.06.2012, Austin, Texas, United States of America

Permalink: https://www.hzdr.de/publications/Publ-17123
Publ.-Id: 17123


Prompt pre-thermal laser ion sheath acceleration with ultra-short laser pulses

Zeil, K.; Bussmann, M.; Cowan, T. E.; Kluge, T.; Kraft, S.; Metzkes, J.; Schramm, U.

Recent laser-ion acceleration experiments performed at the 150 TW Draco laser in Dresden, Germany, have demonstrated the importance of a precise understanding of the electron dynamics in solids on an ultra-short time scale. For example, with ultra-short laser pulses a description based purely on the evolution of a thermal electron ensemble, as in standard TNSA models, is not sufficient anymore. Rather, non-thermal effects during the ultra-short intra-pulse phase of laser-electron interaction in solids become important for the acceleration of ions when the laser pulse duration is in the order of only a few 10s of femtoseconds. While the established maximum ion energy scaling in the TNSA regime goes with the square root of the laser intensity, for such ultra short pulse durations the maximum ion energy is found to scale linear with laser intensity [1], motivating the interest in such laser systems.
Investigating the influence of laser pulse contrast, laser polarization and laser incidence angle on the proton maximum energy and angular distribution, we present recent advances in the description of the laser interaction with solids, focusing on the implications of intra-pulse non-thermal phenomena on the ion acceleration.

  • Invited lecture (Conferences)
    Advanced Accelerator Concepts Workshop, 12.06.2012, Austin, Texas, United States of America

Permalink: https://www.hzdr.de/publications/Publ-17122
Publ.-Id: 17122


High magnetic field study of the Gd-Co exchange interactions in GdCo12B6

Isnard, O.; Skourski, Y.; Diop, L. V. B.; Arnold, Z.; Andreev, A. V.; Wosnitza, J.; Iwasa, A.; Kondo, A.; Matsuo, A.; Kindo, K.

Pulsed magnetic fields up to 68 Tesla have been used to determine the intersublattice coupling strength and its temperature dependence of GdCo12B6 compound. This compound exhibits ferrimagnetic behaviour below 163 ± 2 K. Two antiferromagnetically coupled sublattices cancel out at compensation temperature at about 48 K. They are carrying magnetization of typically 0.42 μB/Co atom and 7 μB/Gd. The intrinsic magnetic properties of the GdCo12B6 compound have been determined by combining low temperature magnetic measurements in both steady and pulsed magnetic field, as well as isofield studies in steady field. At 4.2 K, the magnetization curve of GdCo12B6 is found to reach the full saturation with sum of both sublattice magnetizations for an applied magnetic field of about 68 T. In addition a detailed study is presented in the whole ordered temperature range on the basis of magnetization curves recorded using pulsed magnetic field up to 60 T. This has enabled to investigate the intersublattice coupling strength and its temperature dependence, a value JCo-Gd/kB = −5.3 ± 0.3 K is derived from the magnetization curves whereas one gets much larger value for JCo-Co/kB = 108 K.

Permalink: https://www.hzdr.de/publications/Publ-17121
Publ.-Id: 17121


Variation of the intersublattice exchange coupling due to hydrogen absorption in Er2Fe14B: A high-field magnetization study

Tereshina, E. A.; Tereshina, I. S.; Kuzmin, M. D.; Skourski, Y.; Doerr, M.; Chistyakov, O. D.; Telegina, I. V.; Drulis, H.

Single crystals of a series of hydrides Er2Fe14BHx (x ≤ 2.5) have been produced and studied in pulsed magnetic fields up to 60 T. The magnetization curve of Er2Fe14B in the easy direction [100] features a stepwise anomaly at about 45 T, corresponding to the first-order phase transition. A similar magnetization jump is also present in the curve along [110], but at a higher field, ∼52 T. The [100] data of the parent and hydrogen-charged Er2Fe14BHx with x = 0.25, 1.5, 2.5 were used to deduce the Er-Fe molecular field Hmol as a function of hydrogen content x. After moderate initial decrease, Hmol(x) drops abruptly above x = 1.5. Hydrogenation results in a 12% reduction of the Er-Fe molecular field in Er2Fe14BH2.5 as compared to Er2Fe14B. For reference, influence of hydrogen on Hmol in an Er2Fe17-H system is also presented

Permalink: https://www.hzdr.de/publications/Publ-17120
Publ.-Id: 17120


Efficient Proton Acceleration with Ultra-short Laser Pulses

Zeil, K.; Bussmann, M.; Cowan, T.; Kluge, T.; Metzkes, J.; Schramm, U.; Kraft, S.

We present a systematic investigation of ultra-short pulse laser acceleration of protons yielding unprecedented maximum proton energies of 19 MeV using the Ti:Sa based high power laser (150 TW) Draco at the Helmholtz-Zentrum Dresden-Rossendorf. For plain few micron thick foil targets a linear scaling of the maximum proton energy with laser power is observed and attributed to the short acceleration period close to the target rear surface*. The influence of laser pulse contrast, laser polarization and laser incidence angle on the proton maximum energy and angular distribution has been investigated. The reliability of the system was improved in order to perform radiobiological studies. Additionally, an increase of laser to proton energy conversion efficiency by use of mass limited Au disks with diameters between 20 µm and 100 µm and sub-micron thickness could have been demonstrated.

  • Poster
    IPAC 2012, 23.-25.05.2012, New Orleans, LA, USA

Permalink: https://www.hzdr.de/publications/Publ-17119
Publ.-Id: 17119


Direct observation of prompt pre-thermal laser ion sheath acceleration

Zeil, K.; Metzkes, J.; Kluge, T.; Bussmann, M.; Cowan, T. E.; Kraft, S. D.; Sauerbrey, R.; Schramm, U.

High-intensity laser plasma-based ion accelerators provide unsurpassed field gradients in the megavolt-per-micrometer range. They represent promising candidates for next-generation applications such as ion beam cancer therapy in compact facilities. The weak scaling of maximum ion energies with the square-root of the laser intensity, established for large subpicosecond class laser systems, motivates the search for more efficient acceleration processes. Here we demonstrate that for ultrashort (pulse duration ~ 30 fs) highly relativistic (intensity ~ 10 21 W cm − 2 ) laser pulses, the intra-pulse phase of the proton acceleration process becomes relevant, yielding maximum energies of around 20 MeV. Prominent non-target-normal emission of energetic protons, reflecting an engineered asymmetry in the field distribution of promptly accelerated electrons, is used to identify this pre-thermal phase of the acceleration. The relevant timescale reveals the underlying physics leading to the near-linear intensity scaling observed for 100 TW class table-top laser systems.

Permalink: https://www.hzdr.de/publications/Publ-17118
Publ.-Id: 17118


Efficient proton acceleration with ultra-short laser pulses

Zeil, K.; Bussmann, M.; Cowan, T. E.; Kluge, T.; Kraft, S. D.; Metzkes, J.; Schramm, U.

We present a systematic investigation of ultra-short pulse laser acceleration of protons yielding unprecedented maximum proton energies of 19 MeV using the Ti:Sa based high power laser (150 TW) Draco at the Helmholtz-Zentrum Dresden-Rossendorf. For plain few micron thick foil targets a linear scaling of the maximum proton energy with laser power is observed and attributed to the short acceleration period close to the target rear surface [1]. The influence of laser pulse contrast, laser polarization and laser incidence angle on the proton maximum energy and angular distribution has been investigated.
Although excellent laser pulse contrast was available slight deformations of the target rear were found to lead to a predictable shift of the direction of the energetic proton emission away from target normal towards the laser direction. The change of the emission characteristics are compared to analytical modelling and 2D PIC simulations.
Additionally, an increase of laser to proton energy conversion efficiency by use of mass limited Au disks with diameters between 20 µm and 100 µm and sub-micron thickness could have been demonstrated.

  • Lecture (Conference)
    Laser and Plasma Accelerators Workshop, 22.06.2011, Shanghai, China

Permalink: https://www.hzdr.de/publications/Publ-17117
Publ.-Id: 17117


Fracture mechanics characterisation of the decommissioned WWER-440 reactor pressure vessel of the NPP Greifswald unit 4

Viehrig, H.-W.; Houska, M.; Altstadt, E.; Valo, M.

Nuclear power plant operators must demonstrate that the structural integrity of a nuclear reactor pressure vessel (RPV) is assured during routine operations or under postulated accident conditions. The aging of the RPV steels is monitored via surveillance programs. Radiation loading, metallurgical and environmental histories, however, can differ between surveillance and RPV materials. Therefore, the investigation of RPV material from decommissioned NPPs offers the unique opportunity to evaluate the real toughness response.
The Greifswald units representing the first generation of WWER-440/V-230 reactors were shut down after 11 to 15 years of operation and the RPVs represent different material conditions as follows: Irradiated (Unit 4), irradiated and recovery annealed (Units 2 and 3), and irradiated, recovery annealed and re-irradiated (Unit1). The recovery annealing of the RPV was performed at a temperature of 475° for about 150 hours and includes a region covering ±0.70 m above and below the circumferential core weld.
Material samples of a diameter of 119 mm called trepans were extracted from the RPV walls. The working program is focused on the characterisation of the RPV steels (base and weld metal) across the thickness of the RPV wall. The paper presents an overview about test results measured on the trepans taken from the welding seam SN0.1.4. and forged base metal ring 0.3.1. located in the reactor core region of the Greifswald units 1, 2 and 4 RPV. It comprises chemical analysis, microstructure investigations (by means of metallography, electron microscopy and SANS) and mechanical testing (hardness measurements, tensile, Charpy-V), and fracture mechanics testing. The key part of the testing is focussed on the determination of the reference temperature T0 following the ASTM test standard E1921 to determine the facture toughness, and how it degrades under neutron irradiation.
Following results have been determined:

  • The recovery annealing of the welding seams and base metal could be confirmed.
  • KJc values of the weld metals generally follow the course of the MC though with a large scatter.
  • There is a large variation in the T0 values evaluated across the thickness of the multilayered welding seams. The T0 measured on TS oriented SE(B) from different thickness locations of the welding seams strongly depends on the structure along the crack tip.
  • A strong scatter of the fracture toughness KJc values of the irradiated (unit 4) and recovery annealed base (unit 1) metal of is observed with clearly more than 2% of the values below the fracture toughness curve for 2% fracture probability.
  • It was demonstrated that T0 evaluated according to the SINTAP MC extension represents the brittle fraction of the data sets.
  • The application of the Unified Curve concept gave T0 values comparable to the standard MC approach, but the slope of the fracture toughness temperature curve is more shallow for highly embrittled conditions.
  • The embrittlement of the unit 4 base and weld metal does not follow the prediction according to the Russian code PNAE G-7-008-86.

Keywords: reactor pressure vessel steel; neutron embrittlement; fracture toughness; Master Curve; integrity assessment; prediction

  • Contribution to proceedings
    12th International Conference “Material Issues in Design, Manufacturing and Operation of Nuclear Power Plants Equipment", 04.-08.06.2012, St. Petersburg, Russia
    Proceedings of the 12th International Conference “Material Issues in Design, Manufacturing and Operation of Nuclear Power Plants Equipment", St. Petersburg: Prometey Institute St. Petersburg

Permalink: https://www.hzdr.de/publications/Publ-17116
Publ.-Id: 17116


New iron(III) nitrate hydrates: Fe(NO3)3•xH2O with x = 4, 5 and 6

Schmidt, H.; Asztalos, A.; Bok, F.; Voigt, W.

Crystals of the title compounds were grown from their hydrous melts or solutions. The crystal structure of iron(III) trinitrate hexahydrate {hexaaquairon(III) trinitrate, [Fe(H2O)6](NO3)3} is built up from [Fe(H2O)6]2+ octahedra and nitrate anions connected via hydrogen bonds. In iron(III) trinitrate pentahydrate {pentaaquanitratoiron(III) dinitrate, [Fe(NO3)(H2O)5](NO3)2}, one water molecule in the coordination octahedron of the FeIII atom is substituted by an O atom of a nitrate group. Iron(III) trinitrate tetrahydrate {triaquadinitratoiron(III) nitrate monohydrate, [Fe(NO3)2(H2O)3]NO3H2O} represents the first example of a simple iron(III) nitrate with pentagonal–bipyramidal coordination geometry, where two bidentate nitrate anions and one water molecule form a pentagonal plane.

Permalink: https://www.hzdr.de/publications/Publ-17115
Publ.-Id: 17115


Microbiological analysis of the in situ Bitumen-Nitrate-Opalinus Clay interaction

Moors, H.; Boven, P.; Geissler, A.; Selenska-Pobell, S.; Leys, N.

Clay formations like the Opalinus Clay are foreseen to serve as the host rock for geological disposal of high- and intermediate-level long-lived radioactive waste in several countries, because of their favourable properties to delay the migration of radionuclides over time. However, bituminized intermediate-level long-lived radioactive waste may physico-chemically perturb the clay barrier properties because in time it will leach substantial amounts of nitrate and organic bitumen degradation products (BDP).
To study the physico-chemical impact of intermediate-level radioactive waste containing bitumen and nitrate, an in situ experiment in the Opalinus Clay (Saint Ursanne, Switzerland) named the Bitumen-Nitrate-Clay interaction (BN) experiment, is being performed at the Mont Terri Rock Laboratory. The in situ equipment of the BN-experiment consists of three separate packed-off intervals, supplied with a filter screen. Each interval is equipped with its own stainless steel water circulation unit. Such water circulation unit contains water sampling containers, circulation pumps and flow meters. One of the circulation units is equipped with an on-line UV spectrophotometer and pH electrode intervals, allowing a continuous monitoring of nitrate, nitrite concentrations, organic carbon level and pH.
In a first series of tests, the microbial and biogeochemical effect of a nitrate and/or acetate perturbation is studied. Acetate is used as it a good representation of BDP. Hereto, nitrate was injected in interval 1 while a mixture of nitrate and acetate is injected in interval 2. As an active microbial community can have a significant impact on the physical and (geo)chemical conditions of the clay surrounding the disposal gallery, microbial analyses were performed on samples taken from the interval solutions before, during and after this first series of tests. Our microbial investigations which included Scanning Electron Microscopy, molecular biology methods, ATP-measurements, and cultivation based techniques of the initial pore water samples, proved the presence and activity of bacteria.
Analysis of the 16S rDNA sequences obtained from the initial interval solutions, i.e. artificial pore water used to fill the intervals and which have been in contact with the surrounding clay for more than six months, indicates similar bacterial communities in all three solutions of the test intervals with the dominant population being Proteobacteria (81.5 – 94.9 %) and Firmicutes (3.4 – 11.1%). Actinobacteria (1.7 and 7.4%) have only been detected in the initial pore water of two intervals.
The first results of the Ribosomal Intergenic Spacer Amplification (RISA) analysis, using universal bacterial primers for 16S rDNA968-983 and 23S rDNA115-130, demonstrate that in both injection tests, i.e. nitrate (interval 1) or nitrate and acetate (interval 2), a strong shift in bacterial communities was induced. Just before the start of these injection tests the pore waters of the two intervals were strongly predominated by different Clostridial species most of them related to Desulfosporosinus species. In addition, smaller populations of Bacteroidetes and Beta– proteobacteria were found as well. Twenty-four hours later, a rapid and strong proliferation of Bacteroidetes, in interval 1, and of Alphaproteobacteria, in intervals 1 and 2, occurred. Specific for interval 1, a stimulation of Beta– and Deltaproteobacteria and a complete masking of the Clostridial groups had occured. In contrast, in interval 2, Gammaproteobacteria were stimulated and some Clostridia continued to persist. This shift may be due to bacterial contamination of the exchanged interval solutions and/or the drastic change of carbon– and/or electron acceptor source.

Keywords: opalinus clay; microbial communities; 16S rDNA retrieval; RISA analyses

  • Poster
    Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, 22.-25.10.2012, Montpellier, France

Permalink: https://www.hzdr.de/publications/Publ-17114
Publ.-Id: 17114


Coherent THz pulses from linear SRF accelerators: Perspectives for naturally synchronized THz pump probe experiments and novel electron beam diagnostic

Gensch, M.

At the ELBE accelerator at the HZDR a new electron beamline, providing for femtosecond electron bunches with nC bunch charges and repetition rates in the 1 – 200 KHz regime is currently constructed. The 40 MeV electrons will be used in photon-electron interaction experiments with TW and PW class laser and for the generation of broad band and narrow bandwidth coherent THz pulses in the frequency range between 0.1 THz – 3 THz. Similar to previous work at the prototype THz pump probe facility at FLASH [1,2] the natural synchronization between light pulses generated by the same electron bunch shall be employed for fully synchronized experiments between narrow and broad band THz pulses. The pulse energies are expected to exceed the 100 microJ limit at scalable repetition rates between 1 and 200 KHz (cw), thereby the coherent THz facility will represent a worldwide unique facility. Besides user experiments the laboratory is also foreseen as a test bed for THz-based electron bunch diagnostics (arrival time, bunch form, …) on cw linear accelerators. The current status of the project and planned experiments are presented.
[1] M. Gensch et. al., The new THz undulator beamline at FLASH, Infrared Phys. Technol. 51 (2008), 423.
[2] U. Fruehling, M. Wieland, M. Gensch et. al., Single-shot Terahertz-field driven Streak camera, Nature Photonics 3 (2009), 523.
[3] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch et. al., Few Femtosecond Timing at 4th Generation X-ray light sources, Nature Photonics 5 (2011), 162."

  • Invited lecture (Conferences)
    Workshop on Terahertz Sources for Time Resolved Studies of Matter, 30.-31.07.2012, Chicago, USA

Permalink: https://www.hzdr.de/publications/Publ-17113
Publ.-Id: 17113


Age and Genesis of Greisen Mineralization in the Li-Sn(-W) Deposit Zinnwald, Eastern Erzgebirge, Germany

Atanasova, P.; Gutzmer, J.; Seifert, T.; Pfänder, J.

The Zinnwald greisen-type ore deposit forms part of the Altenberg-Teplice caldera in the eastern part of Saxony, Germany. Flat dipping quartz-zinnwaldite-topaz-fluorite-cassiterite greisen ore bodies and veins are hosted in the uppermost part of the “small intrusion” Zinnwald Li-F-granite stock (cf. Seifert & Kempe, 1994). The current investigation was aimed to provide new insight into the metallogenesis of the deposit and its temporal and genetic relation to the late Variscan magmatic evolution of the Altenberg-Teplice Caldera.
Greisen-type mineralization in Zinnwald is the product of high temperature post-magmatic hydrothermal alteration (i.e., greisenization), which affected and overprinted the uppermost part of the narrow Zinnwald granite stock. Pertrographic and mineral paragenetic evidence is used to illustrate that the genesis of the greisen mineralization is related to the interaction of a felsic igneous protolith with aqueous magmatic fluids, highly enriched in alkali metals, incompatible elements and volatiles, such as F. The chemical and mineralogical effects of greisenization are subdivided into three different stages, reflecting in a logical sequence the predicted physicochemical evolution of a magmatic hydrothermal fluid system.
A model is suggested that predicts upward directed fluid flow explaining the characteristic textural and geochemical alteration patterns within the granite stock, as well as high rare metal contents of the Zinnwald granite and provides a possible solution for the problem of fluid access to the solidified granite cap. This holistic metallogenetic model for the origin of the Zinnwald Li-Sn(-W) deposit integrates available field geological, geochronological, petrological and geochemical data and is largely based on the Burnham (1997) model for porphyry deposits, on the Shcherba (1970) model for greisen deposits, but augmented by peculiarities of greisen-type ore deposits of the Erzgebirge.
Zinnwaldite mica separates from the Zinnwald greisen dated in this study yield an average age of 314.1 ± 1.5 Ma. This age is significantly younger than available intrusion ages of similar A-type granitic intrusions into the Teplice Rhyolite (TR) such as 324 ± 2 Ma Re–Os molybdenite age for the Altenberg granite (Romer et al. 2007). The Ar-Ar age is thought to reflect cooling of the greisen below the closure temperature of zinnwaldite, estimated to be about 373 ± 21°C (closure temperature of biotite, Berger & York 1981). In this case, the Ar-Ar age obtained is a minimum age estimate for Li-Sn(-W) mineralization, known to have formed at temperatures above this closure temperature. Ore formation is regarded as an integral part of the development of the Altenberg-Teplice caldera and associated with the intrusion of peraluminous A-type Li-mica granites in an extensional post-orogenic environment during the later stage of the Variscan Orogeny.

Keywords: Zinnwald; Lithium; Greisen

  • Abstract in refereed journal
    Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften (2012)80, 72-72
  • Lecture (Conference)
    GeoHannover 2012, 01.-03.10.2012, Hannover, Deuschland

Permalink: https://www.hzdr.de/publications/Publ-17112
Publ.-Id: 17112


(THz based) Electron Bunch Diagnostic at Superconducting Continuous Wave Accelerators

Caglar, K.; Mamidala, V.; Lehnert, U.; Schneider, C.; Seidel, W.; Schlarb, H.; Kuntzsch, M.; Staats, G.; Al-Shemmary, A.; Stojanovic, N.; Geloni, G.; Helm, M.; Michel, M.; Gensch, M.

At the srf based prototype cw accelerator ELBE a new electron beamline, providing for femtosecond electron bunches with nC bunch charges and repetition rates in the 1 – 200 KHz regime and with pC bunch charge and repetition rates of 13 MHz is currently constructed. The 40 MeV electrons will be used in photon-electron interaction experiments with TW and PW class laser and the generation of broad band and narrow bandwidth coherent THz pulses. In this paper we outline ideas for novel online diagnostics of the electron bunch properties (e.g. arrival time and bunch form) based on the time and frequency domain analysis of the emitted coherent THz radiation but also based on direct measurements by e.g. electro-optic sampling. The suitability of ELBE as a testbed for diagnostic of future cw X-ray photon sources (e.g. energy recovery linacs) will be discussed.

  • Poster
    IPAC 2012 - International Particle Accelerator Conference 2012, 21.-25.05.2012, New Orleans, USA

Permalink: https://www.hzdr.de/publications/Publ-17111
Publ.-Id: 17111


Evaluation of tomographic data

van den Hoff, J.

kein Abstract verfügbar

  • Book chapter
    R. Salzer: Biomedical Imaging: Principles and Applications, New York: Wiley, 2012, 978-0-470-64847-6, 30-62

Permalink: https://www.hzdr.de/publications/Publ-17110
Publ.-Id: 17110


Interaction of Uranium(VI) with Bioligands Present in Human Biological Fluids: The Case Study of Urea and Uric Acid

Osman, A. A. A.; Geipel, G.; Bernhard, G.

The complexation of uranium(VI) with bioligands that found in human biological fluids, viz, urea and uric acid in aqueous solutions has been investigated using time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature, I = 0.1 M (NaClO4) and pH (3 for uric acid; 4 for urea). In both complex systems a static quench effect with increasing ligand concentration and no peaks shift upon complexation were observed. With uranium(VI) both ligands formed a fairly weak 1:1 complex with av-erage stability constants of log β110 = 4.67 ± 0.29 for uric acid and log β110 = 3.79 ± 0.15 and 2.12 ± 0.18 for relatively low and relatively high urea concentrations, re-spectively. Application of the newly generated data on the U(VI) speciation modelling in biofluids, e.g., human urine was also discussed.

Keywords: uranium(VI); urea; uric acid; complexation; stability constant; TRLFS; biofluids; speciation modelling

Permalink: https://www.hzdr.de/publications/Publ-17109
Publ.-Id: 17109


Charakterisierung von Wirt/Gast-Systemen mittels Radiotracertechnik

Stephan, H.

kein Abstract verfügbar

  • Lecture (Conference)
    Institutsseminar, Freie Universität Berlin, Institut für Chemie und Biochemie, 11.05.2012, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17108
Publ.-Id: 17108


Coherent THz Radiation from linear accelerators and 4th Generation X-ray Light sources: Status, Challenges and Diagnostic opportunities

Gensch, M.

The past fifteen years have seen a rapid development of novel techniques to generate and detect ultra-short and high power THz pulses. The availability of these pulses with electric field strength in the few 10 to 100 MV/m regime has led to a number of exciting experiments in particular in the field of non-linear THz spectroscopy and THz control experiments. One class of these THz generation techniques utilizes highly charged, ultra short electron bunches accelerated to relativistic speed in linear particle accelerators [1]. A variety of different source concepts allows to shape the THz pulses from single cycle/broad band pulses to multicycle/narrow-bandwidth pulses with polarizations ranging from radial to linear. One main attraction of accelerator-based THz originates from the fact that the THz generation process does not take place in a medium but in the ultra-high vacuum of the accelerator, so that the THz pulse energy can hence theoretically much easier up scaled than in any of the table top sources available today. Additionally it could recently be shown that coherent THz radiation can be generated residually and in parallel to the femtosecond X-ray pulses in 4th Generation X-ray Light sources such as FLASH [2,3,and 4] and LCLS [5]. This opens up the exciting opportunity to perform naturally synchronized THz pump X-ray probe experiments on few femtosecond time scales [2,3,and 5], the THz sources furthermore constitute an ideal tool for online diagnostic on the electron bunch form at superconducting linear accelerators. An overview over different THz facility projects will be presented and experimental and diagnostic opportunities as well as challenges will be discussed on the example of recent pilot experiments.

[1] G.L. Carr et. al., High power terahertz radiation from relativistic electrons, Nature 420 (2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol. 51 (2008), 423.
[3] U. Fruehling et. al., Single-Shot THz-field-driven X-ray streak camera, Nat. Photon. 3 (2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray Light sources, Nat. Photon. 5 (2011), 162.
[5] D. Daranciang et. al., Single-cycle terahertz pulses with > 0.2 V/angstrom field amplitudes via coherent transition radiation, Appl. Phys. Lett. 99 (2011), 141117.

  • Invited lecture (Conferences)
    Kolloquium des Physik Fakultät der Universität Siegen, 03.05.2012, Siegen, Germany

Permalink: https://www.hzdr.de/publications/Publ-17107
Publ.-Id: 17107


Synthesis and characterization of novel tetrahedral copper(I) complexes comprising tridentate PNP-aminodiphosphines and tetradentate PN(X)P-substituted aminodiphosphines (X = O, S)

Peruzzo, V.; Pretzsch, C.; Tisato, F.; Porchia, M.; Refosco, F.; Marzano, C.; Gandin, V.; Schiller, E.; Walther, M.; Pietzsch, H.-J.

Two series of novel tetrahedral copper(I) complexes comprising tridentate PNP-aminodiphosphines and tetradentate PN(X)P-substituted aminodiphosphines (X = O, S) have been prepared and characterized by conventional physico-chemical techniques. The first series includes ‘3 + 1’-type complexes comprising an aromatic PNP-aminodiphosphine and acetonitrile or triphenylphosphine. In the second series, the central amine function of the PNP-ligand was substituted with functionalized pendant arms containing ether, hydroxyl or thioether groups to enhance the chelation ability of the ligand. Fully coordinated neutral and cationic complexes were isolated. A preliminary study investigating both the labeling of 64Cu with the prototype PN(S)P ligand and the potential cytotoxic activity of the ‘cold’ [Cu(PN(S)P)][BF4] complex is reported.

Permalink: https://www.hzdr.de/publications/Publ-17106
Publ.-Id: 17106


Synthesis, in vitro and in vivo characterization of novel 99mTc-‘4+1’-labeled 5-nitroimidazole derivatives as potential agents for imaging hypoxia

Giglio, J.; Fernández, S.; Pietzsch, H.-J. D.; Dematteis, S.; Moreno, M.; Pacheco, J. P.; Cerecetto, H.; Rey, A.

The evaluation of oxygenation status of solid tumors is an important field of radiopharmaceutical research. With the aim to develop new potential 99mTc-radiopharmaceuticals for imaging hypoxia, we have synthesized two novel isocyanide derivatives of metronidazole, which has demonstrated high affinity for hypoxic tumors in vitro and in vivo.
Methods: Metronidazole derivatives 4-isocyano-N-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]butanamide (M1) and 1-(4-isocyanobutanoyl)-4-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]piperazine (M2) were synthesized, and labeling was performed through preparation of their corresponding 99mTc-(4+1) complexes, 99mTc-NS3M1 and 99mTc-NS3M2. The structure of the technetium complexes was corroborated by preparation and characterization of the corresponding rhenium complexes. We have studied the main physicochemical properties (stability, lipophilicity and plasma protein binding). Biological behavior in HCT-15 cells both in oxia and in hypoxia was assessed.
Biodistribution in normal mice and in animals bearing induced 3LL Lewis murine lung carcinoma was also studied.
Results: Metronidazole derivatives were successfully synthesized. Labeling with high radiochemical purity was achieved for both ligands.
99mTc complexes were stable in labeling milieu and human plasma. However, presence of the piperazine linker in M2 resulted in higher lipophilicity and protein binding. Although cell uptake in hypoxic conditions was observed for both radiotracers, 99mTc-NS3M2 biodistribution was considered unsuitable for a potential radiopharmaceutical due to high liver uptake and poor blood clearance. However, 99mTc-NS3M1 demonstrated a very favorable in vivo profile both in normal mice and in mice bearing induced tumors.
Conclusion: Selective uptake and retention in tumor together with favorable tumor/muscle ratio make 99mTc-NS3M1 a promising candidate for further evaluation as potential hypoxia imaging agent in tumors.

Permalink: https://www.hzdr.de/publications/Publ-17105
Publ.-Id: 17105


Brilliant Infrared Light Sources for Micro-Ellipsometric Studies of Organic Thin Films

Gensch, M.

Micro-ellipsometric studies in the infrared and THz spectral range are of increasing interest in particular for the determination of the optical constants of organic films and multilayers as in these cases the composition, thickness or roughness often vary on micro- and mesoscopic length scales. In cases where the aforementioned properties change across the probed spot, the degree of polarization of the reflected beam is deteriorated and sophisticated models have to be employed to derive the optical constants or other parameters from the determined ellipsometric angles. The achievable spot size in an ellipsometric set-up is now limited by the necessity to perform a specular reflectance measurement with a reasonably defined angle. In the optimal case the infrared radiation can be focused to near diffraction limited spot sizes with opening angles in the incoming beam of less than 7°. In other words such an experiment turns out to be limited by a source property that is typically called brilliance or brightness and makes the technique particularly suited for the use of accelerator based infrared sources such as 3rd generation synchrotron storage rings. The current status of such activities worldwide will be reviewed and discussed on the example of different pilot experiments and an outlook on future developments will be given.

Keywords: Brilliance; Brightness; infrared; THz; polymer brushes; degree of polarization; diffraction limit

  • Book chapter
    K. Hinrichs, K. Eichhorn: Ellipsometry of Functional Organic Surfaces and Films, Berlin: Springer, 2014, 978-3-642-40128-2, 325-336
    DOI: 10.1007/978-3-642-40128-2_16

Permalink: https://www.hzdr.de/publications/Publ-17104
Publ.-Id: 17104


Coherent THz Radiation from linear accelerators and 4th Generation X-ray Light sources: Status, Challenges and Opportunities

Gensch, M.

The past fifteen years have seen a rapid development of novel techniques to generate and detect ultra-short and high power THz pulses. The availability of these pulses with electric field strength in the few 10 to 100 MV/m regime has led to a number of exciting experiments in particular in the field of non-linear THz spectroscopy and THz control experiments. One class of these THz generation techniques utilizes highly charged, ultra short electron bunches accelerated to relativistic speed in linear particle accelerators [1]. A variety of different source concepts allows to shape the THz pulses from single cycle/broad band pulses to multicycle/narrow-bandwidth pulses with polarizations ranging from radial to linear. One main attraction of accelerator-based THz originates from the fact that the THz generation process does not take place in a medium but in the ultra-high vacuum of the accelerator, so that the THz pulse energy can hence theoretically much easier up scaled than in any of the table top sources available today. Additionally it could recently be shown that coherent THz radiation can be generated residually and in parallel to the femtosecond X-ray pulses in 4th Generation X-ray Light sources such as FLASH [2,3,and 4] and LCLS [5]. This opens up the exciting opportunity to perform naturally synchronized THz pump X-ray probe experiments on few femtosecond time scales [2,3,and 5]. An overview over different THz facility projects will be presented and experimental opportunities and challenges will be discussed on the example of recent pilot experiments.

[1] G.L. Carr et. al., High power terahertz radiation from relativistic electrons, Nature 420 (2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol. 51 (2008), 423.
[3] U. Fruehling et. al., Single-Shot THz-field-driven X-ray streak camera, Nat. Photon. 3 (2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray Light sources, Nat. Photon. 5 (2011), 162.
[5] D. Daranciang et. al., Single-cycle terahertz pulses with > 0.2 V/angstrom field amplitudes via coherent transition radiation, Appl. Phys. Lett. 99 (2011), 141117.

  • Invited lecture (Conferences)
    Kolloquium des Fachbereichs Physik der Freien Unisversität Berlin, 27.04.2012, FU Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-17103
Publ.-Id: 17103


Design, Evaluation, and Comparison of Ghrelin Receptor Agonists and Inverse Agonists as Suitable Radiotracers for PET Imaging

Chollet, C.; Bergmann, R.; Pietzsch, J.; Beck-Sickinger, A. G.

Ghrelin agonist and inverse agonist radiotracers, suitable for positron emission tomography (PET), were developed to study the behavior of ghrelin receptor ligands in vivo and for further design of druggable peptides. The target peptides were synthesized on solid support and conjugated to the bifunctional chelator 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA), which is known to form a stable complex with Ga3+. Complexation with 68Ga could be achieved under mild conditions and led to radiotracers with high radiochemical purity and specific activity. The biological activity of the radiotracers was evaluated in vitro by an inositol phosphate turnover assay. Pharmacokinetic profile and metabolic stability of the 68Ga-NODAGA-radiotracers were investigated by small animal PET in rodent. Ghrelin derived agonists presented very high kidney accumulation, negligible tissue distribution, fast blood clearance, and poor stability in blood. Contrarily, the inverse agonist radiotracer exhibited very high stability in blood, large diffusion in tissues, reasonable kidney and liver metabolism, and slow blood clearance. This pharmacokinetic profile makes the ghrelin inverse agonist motif KwFwLL-CONH2 suitable for further development of radiotracers and a promising lead to design peptide-based therapeutics against obesity.

Permalink: https://www.hzdr.de/publications/Publ-17102
Publ.-Id: 17102


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