Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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Only approved publications

31738 Publications
The IR and THz Free Electron Laser at the Fritz-Haber-Institut
Schoellkopf, W.; Erlebach, W.; Gewinner, S.; Heyne, G.; Junkes, H.; Liedke, A.; Meijer, G.; Platschkowski, V.; von Helden, G.; Jordan, K.; Rathke, J.; Todd, A. M. M.; Young, L. M.; Bluem, H.; Dowell, D.; Lange, R.; Davidsaver, M.; Lehnert, U.; Michel, P.; Seidel, W.; Wuensch, R.; Loos, H.; Gottschalk, S. C.;
A mid-infrared oscillator FEL with a design wavelength range from 4 to 50 μm has been commissioned at the Fritz-Haber-Institut in Berlin, Germany, for applications in molecular and cluster spectroscopy as well as surface science. The accelerator consists of a thermionic gridded electron gun, a subharmonic buncher and two S-band standing-wave copper structures. The device was designed to meet challenging specifications, including a final energy adjustable in the range of 15 to 50 MeV, low longitudinal emittance (< 50 keV-psec) and transverse emittance (< 20 Pi mm-mrad), at more than 200 pC bunch charge with a micro pulse repetition rate of 1 GHz and a macro pulse length of up to 15 μs. Two isochronous achromatic 180 degree bends deliver the beam to the undulators, only one of which is presently installed, and to the beam dumps. Calculations of the FEL gain and IR-cavity losses predict that lasing will be possible in the wavelength range from less than 4 to more than 50 μm. First lasing was achieved at a wavelength of 16 μm in 2012*. We will describe the FEL system design and performance, provide examples of lasing, and touch on the first anticipated user experiments.

*W. Schoellkopf et al., MOOB01, Proc. FEL 2012
  • Poster
    35th International Free Electron Laser Conference 2013, 26.-30.08.2013, New York, USA
  • Open Access LogoContribution to proceedings
    35th International Free Electron Laser Conference 2013, 26.-30.08.2013, New York, USA
    Proceedings of 35th International Free-Electron Laser Conference, 978-3-95450-126-7, 657-660

Publ.-Id: 19309 - Permalink

RANS (Reynolds Averaged Navier-Stokes) und LES (Large Eddy Simulations) of the Air-Water TOPFLOW-PTS Experiment
Niceno, B.; Lumpp, T.; Apanasevich, P.; Lucas, D.;
The occurrence of a PTS in a reactor vessel is an important phenomenon for assessing nuclear reactor safety. New experiment was conducted at HZDR, focused on thermal mixing processes in the cold leg and the downcomer of two-phase PTS case. Present work reports CFD analysis of steady-state air-water case. CFD analysis was conducted with two turbulence-modeling approaches, RANS and LES. Multiphase situation was modeled with VOF approach. Simulations were performed using the ANSYS Fluent 12 package. Comparison of computed temperatures results and measurements along the thermo-couple lines revealed results depend on the turbulence model used.
Keywords: CFD, Pressurized thermal shock, LES, RANS
  • Journal of Energy and Power Engineering 7(2013)7, 1231-1237

Publ.-Id: 19308 - Permalink

Numerical investigations of direct-contact heat and mass transfer
Apanasevich, P.;
The current project focuses on stratified two-phase flows with heat and mass transfer across a moving interface due to direct contact condensation (DCC) in horizontal pipes or channels.
Keywords: Direct-contact condensation, Direct Numerical Simulatioln (DNS), Large Eddy Simulation (LES)
  • Poster
    HZDR PHD-Seminar, 07.-09.10.2013, Bautzen, Deutschland

Publ.-Id: 19307 - Permalink

Synthesis and radiopharmacological evaluation of 64Cu-labeled bombesin analogs featuring a bis(2-pyridylmethyl) 1,4,7-triazacyclononane chelator
Bergmann, R.; Ruffani, A.; Graham, B.; Spiccia, L.; Steinbach, J.; Pietzsch, J.; Stephan, H.;
The bifunctional chelating agent 2-[4,7-bis(2-pyridylmethyl)-1,4,7-triazacyclononan-1-yl]acetic acid, DMPTACN-COOH, has been found to bind strongly to copper(II), resulting in a radiocopper(II)-ligand complex that exhibits high in vivo stability. The pendant carboxylic acid group enables this derivative to be conjugated to the N-terminal amino acid residues of peptides. Exploiting this, two stabilized bombesin (BBN) derivatives, ßAla-ßAla-[Cha13,Nle14]BBN(7-14) and ßhomo-Glu-ßAla-ßAla-[Cha13,Nle14]BBN(7-14) have been coupled to DMPTACN-COOH and radiolabeled with the positron emitter copper-64 (64Cu-1 and 64Cu-3). The in vitro binding characteristics of the [64Cu]Cu-labeled bombesin conjugates in gastrin-releasing peptide receptor (GRPR) over-expressing prostate cancer (PC-3) cells have been evaluated. Biodistribution studies performed in Wistar rats indicate a specific uptake in the GRPR-rich pancreas and rapid renal elimination for both 64Cu-1 and 64Cu-3. Small animal PET imaging studies performed in NMRI nu/nu mice bearing the human prostate tumor PC-3 demonstrated a very high degree of tumor accumulation for 64Cu-1 and 64Cu-3. Incorporation of a single additional glutamic acid residue within the spacer between bombesin and the radiolabeled complex (64Cu-3) leads to a higher tumor-to-muscle uptake ratio (amounting to >30 at 100 min post injection) compared to 64Cu-1.

Publ.-Id: 19306 - Permalink

Design, synthesis, characterisation and in vitro studies of hydrophilic, colloidally stable, 64Cu(II)-labelled, ultra-small iron oxide nanoparticles in a range of human cell lines
Pombo Garcia, K.; Zarschler, K.; Barreto, J. A.; Hesse, J.; Spiccia, L.; Graham, B.; Stephan, H.;
The application of ultra-small super-paramagnetic iron oxide nanoparticles (USPIONs) as versatile diagnostic probes for multimodal imaging in biomedicine, including via magnetic resonance imaging (MRI) and positron emission tomography (PET), requires hydrophilic and biocompatible surface coatings. Herein, we describe the development of USPIONs stabilised by octylamine-modified polyacrylic acid (OPA) and the subsequent conjugation of a 64Cu(II) chelator, N-(4-aminophenyl)-2-[4,7-bis(2-pyridylmethyl)-1,4,7-triazacyclononan-1-yl]acetamide (amino-dmptacn), for radioactivity-based detection. Transmission electron microscopic analysis and dynamic light scattering measurements confirmed the monodispersity and stability of the OPA-USPIONs in aqueous media and revealed a hydrodynamic size of ca. 15 nm. Furthermore, the biocompatibility and cellular uptake efficiency of the functionalised USPIONs was investigated in a range of normal and tumour cell lines. The results clearly show a cell type- as well as time-dependent internalisation of the OPA-USPIONs via active energy-dependent pathways. Biocompatibility of OPA-USPIONs in the concentration range of 10–50 μg mL−1 was demonstrated, while impairment of cellular viability was observed for human umbilical vein endothelial cells at 100 μg mL−1. Upon exposure to human serum, several biomolecules cover the negatively-charged surface of the nanoparticles and a biomolecular corona is formed. Nonetheless, the nanoparticles represent a promising platform for the future development of a bimodal PET-MRI tumour-imaging agent.

Publ.-Id: 19305 - Permalink

Towards laser driven proton therapy of cancer: Status of the Dresden program
Kroll, F.; Baumann, M.; Beyreuther, E.; Bussmann, M.; Cowan, T. E.; Enghardt, W.; Kaluza, M.; Karsch, L.; Kluge, T.; Kraft, S. D.; Laschinsky, L.; Metzkes, J.; Nicolai, M.; Oppelt, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Schramm, U.; Schürer, M.; Pawelke, J.; Zeil, K.;
Proton beams by their well-confined energy-loss in matter are a promising tool for the improvement of radiotherapy of cancer and are currently under intense medical investigation. Wider clinical use, however, is limited by the complexity and expense of current proton and ion accelerators. Compact laser driven proton therapy accelerators are discussed as a promising alternative, yet require substantial development in reliable beam generation and transport, but also in dosimetric protocols as well as validation in radiobiological studies.
In our talk, we will present the first direct and dose controlled comparison of the radiobiological effectiveness (RBE) of intense proton pulses from a laser driven accelerator with conventionally generated continuous proton beams, showing no dependence of the RBE on the different beam properties [1]. Controlled dose delivery, precisely online and offline monitored for each of the ~ 4000 proton pulses, resulted in an unprecedented relative dose uncertainty of below 10%, using approaches scalable to radiotherapy applications.
In parallel to the development of laser driven proton therapy accelerators, an advancement in instrumentation for laser driven protons is essential. Most importantly, these new diagnostic tools need to speedwise match the repetition rates of state-of-the-art high power laser systems and need to be adapted to the harsh plasma environment of laser based accelerators, not neglecting their fitment to the properties of laser accelerated proton pulses such as the high flux and the broad energy spectrum.
We will present three types of scintillator-based detectors, all being optimized for specific stages of the experimental chain: a one-dimensional space- and energy-resolved detector for online spectral stability control of the acceleration performance [2], a two-dimensional space- and energy-resolved detector for source characterization measurements, and a three-dimensional detector for precise dose verification in a water-equivalent medium with regards to medical quality assurance [3].

[1] K. Zeil, et al.: Dose-controlled irradiation of cancer cells with laser-accelerated proton pulses, Appl. Phys. B (2012)
[2] J. Metzkes, et al.: A scintillator-based online detector for the angularly resolved measurement of laser-accelerated proton spectra, Review of Scientific Instruments, Rev. Sci. Instrum. 83, 123301 (2012)
[3] F. Kroll, et al.: Preliminary investigations on the determination of three-dimensional dose distributions using scintillator blocks and optical tomography, Med. Phys. 40, 082104 (2013)
  • Lecture (Conference)
    SPIE Optics + Optoelectronics 2013, 15.-18.04.2013, Prag, Tschechische Republik

Publ.-Id: 19304 - Permalink

Geometallurgische Klassifizierung von Seltenen Erden Mineralisation in Alkalinen Komplexen
Atanasova, P.; Gutzmer, J.; Tolosana Delgado, R.; van den Boogaart, K. G.;
Alkaline Komplexe stellen eine der größten und vielversprechendsten Bezugsquellen zur Deckung des zukünftigen Bedarfs an Schweren Seltenen Erden (heavy rare earths, HREE) dar. Neben der oft starken Anreicherung an HREE, sind diese auch an weiteren sogenannten kritischen Metallen angereichert, so zum Beispiel Nb, Ta, Zr, aber auch Ga können erheblich angereichert sein. Diese sehr ungewöhnliche und oft variable Anreicherung einer großen Anzahl von Metallen ist verbunden mit einer ebenso vielfältigen Erzmineralogie und einer oft sehr komplexen Architektur der Lagerstättenkörper. Dies stellt eine Herausforderung für den Abbau und für die spätere Aufbereitung dar.
Zur effizienten Nutzung solcher komplexer Lagerstätten sollen geometallurgische Modelle eingesetzt werden. In geometallurgischen Modellen werden die räumliche Diversität und Variabilität aller Parameter, die für Gewinnung, Aufbereitung und metallurgische Raffination Relevanz haben gemeinsam dargestellt und geometallurgische Domänen definiert. Relevante Parameter sind insbesondere die chemische, mineralogische und mineralchemische Zusammensetzung, aber auch das Mikrogefüge. Basierend auf einem solchen multikriteriellen geometallurgischen Modell können dann Gewinnung und Verarbeitung des Lagerstätteninhalts optimal aufeinander abgestimmt werden. .
Genaue Betrachtung der geologischen Gegebenheiten im Gelände und am Bohrkern, sowie eine flächendeckende Beprobung sind essenziell für das makroskopische Verständnis des Erzkörpers. Mikrotexturen, Mineralogie und Metallverteilung, sowie Mineralassoziationen, Korngröße und Freilegungsgrad sind Schlüsselparameter für die Charakterisierung der Erze und Aufbereitungsprodukte und können mithilfe von Rasterelektronenmikroskop-basierte Bildbearbeitung erfasst und für die Erstellung des geometallurgischen Models genutzt werden.
Die Anwendbarbeit und der Nutzen eines solchen Models sind hier am Beispiel des Norra Kärr Alkalinen Komplexes beispielhaft illustriert. Das Vorkommen befindet sich in Südschweden, ca. 300 km südwestlich von Stockholm und 15 km nördlich der Stadt Gränna. Mit einer Oberflächenausdehnung von ca. 350 m x 1100 m und nachgewiesene Ressourcen von 41.6 Mt @ 0.57 % TREO mit 51 % HREO ist das Vorkommen sehr gut exploriert und zeigt erhebliche texturelle und kompositionelle Variabilität. Die Mineralisation findet sich in stark deformierten und verfalteten Aegirin Nephelin-Syeniten. Minerale der Eudialytgruppe sind Haupterzträger, mit Mosandrit und Britholit in untergeordneten Mengen. Die Lagerstätte eignet sich aufgrund seiner Variabilität und des sehr guten Erkundungsstandes sehr gut für eine geometallurgische Modellierung.
  • Poster
    Aufbereitung und Recycling 2013, 13.-14.11.2013, Freiberg, Deutschland
  • Contribution to proceedings
    Aufbereitung und Recycling 2013, 13.-14.11.2013, Freiberg, Deutschland

Publ.-Id: 19303 - Permalink

Program and status for the planned underground accelerator in the Dresden Felsenkeller
Bemmerer, D.; Akhmadaliev, S.; Al-Abdullah, T.; Anders, M.; Cowan, T. E.; Elekes, Z.; Junghans, A. R.; Gohl, S.; Krause, J.; Reinhardt, T. P.; Reinicke, S.; Rimarzig, B.; Röder, M.; Schmidt, K.; Schwengner, R.; Szücs, T.; Takács, M.; Wagner, A.; Wagner, L.; Wielicki, J.; Zuber, K.;
The scientific program and curent status of the planned accelerator laboratory in the Felsenkeller shallow-underground facility in Dresden, Germany, are reviewed.
Keywords: Felsenkeller underground accelerator nuclear astrophysics

Publ.-Id: 19302 - Permalink

Precise study of the supernova reaction 40Ca(α,γ)44Ti in the Dresden Felsenkeller
Bemmerer, D.;
Resonance strengths in the supernova reaction 40Ca(α,γ)44Ti have been studied by activation, using underground counting in the Dresden Felsenkeller.
Keywords: Nuclear Astrophysics Supernova Felsenkeller activation measurement alpha-rich freezeout
  • Lecture (Conference)
    EuroGENESIS Final Meeting, 11.-15.06.2013, Barcelona, Spanien

Publ.-Id: 19301 - Permalink

5 MV underground accelerator in the Dresden Felsenkeller
Bemmerer, D.;
Nuclear reaction studies by in-beam gamma-spectroscopy with a low expected signal counting rate are best performed in a low-background environment. At gamma-ray energies above 3 MeV that are typical of many nuclear reactions, the background is given by cosmic-ray effects. Thick layers of rock absorb cosmic-ray muons and thus attenuate these effects.

At the Felsenkeller underground site in Dresden, shielded by 47 m of rock, the cosmic-ray muon flux is reduced by a factor of 30. It has recently been shown that additional active shielding brings the total background suppression factor to several hundred, creating an attractive environment for nuclear reaction studies for astrophysics and applications.

A 5 MV Pelletron tandem accelerator with double charging chains was recently purchased for installation in Felsenkeller and has already been transported to Dresden. Recent progress of the project will be reviewed, and an outlook will be given.
Keywords: Underground accelerator Felsenkeller Nuclear astrophysics
  • Invited lecture (Conferences)
    Nuclear Physics in Astrophysics VI, 20.-24.05.2013, Lisboa, Portugal

Publ.-Id: 19300 - Permalink

Beyond the neutron drip line: The unbound oxygen isotopes O-25 and O-26
Caesar, C.; Simonis, J.; Adachi, T.; Aksyutina, Y.; Alcantara, J.; Altstadt, S.; Alvarez-Pol, H.; Ashwood, N.; Aumann, T.; Avdeichikov, V.; Barr, M.; Beceiro, S.; Bemmerer, D.; Benlliure, J.; Bertulani, C.; Boretzky, K.; Borge, M.; Burgunder, G.; Caamano, M.; Casarejos, E.; Catford, W.; Cederkall, J.; Chakraborty, S.; Chartier, M.; Chulkov, L.; Cortina-Gil, D.; Pramanik, U.; Fernandez, P.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; Fraile, L.; Freer, M.; Freudenberger, M.; Fynbo, H.; Galaviz, D.; Geissel, H.; Gernhauser, R.; Golubev, P.; Diaz, D.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Holl, M.; Holt, J.; Ickert, G.; Ignatov, A.; Jakobsson, B.; Johansson, H.; Jonson, B.; Kalantar-Nayestanaki, N.; Kanungo, R.; Kelic-Heil, A.; Knobel, R.; Kroll, T.; Krucken, R.; Kurcewicz, J.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lepyoshkina, O.; Lindberg, S.; Machado, J.; Marganiec, J.; Maroussov, V.; Menendez, J.; Mostazo, M.; Movsesyan, A.; Najafi, A.; Nilsson, T.; Nociforo, C.; Panin, V.; Perea, A.; Pietri, S.; Plag, R.; Prochazka, A.; Rahaman, A.; Rastrepina, G.; Reifarth, R.; Ribeiro, G.; Ricciardi, M.; Rigollet, C.; Riisager, K.; Roder, M.; Rossi, D.; Del Rio, J.; Savran, D.; Scheit, H.; Schwenk, A.; Simon, H.; Sorlin, O.; Stoica, V.; Streicher, B.; Taylor, J.; Tengblad, O.; Terashima, S.; Thies, R.; Togano, Y.; Uberseder, E.; van de Walle, J.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Wheldon, C.; Wilson, G.; Wimmer, C.; Winfield, J.; Woods, P.; Yakorev, D.; Zhukov, M.; Zilges, A.; Zoric, M.; Zuber, K.;
The very neutron-rich oxygen isotopes O-25 and O-26 are investigated experimentally and theoretically. The unbound states are populated in an experiment performed at the R3B-LAND setup at GSI via proton-knockout reactions from F-26 and F-27 at relativistic energies around 442 and 414 MeV/nucleon, respectively. From the kinematically complete measurement of the decay into O-24 plus one or two neutrons, the O-25 ground-state energy and width are determined, and upper limits for the O-26 ground-state energy and lifetime are extracted. In addition, the results provide indications for an excited state in O-26 at around 4 MeV. The experimental findings are compared to theoretical shell-model calculations based on chiral two- and three-nucleon (3N) forces, including for the first time residual 3N forces, which are shown to be amplified as valence neutrons are added.

Publ.-Id: 19299 - Permalink

Superconductivity and magneto-resistance oscillations in amorphous Ga films
Skrotzki, R.; Herrmannsdörfer, T.; Schönemann, R.; Heera, V.; Fiedler, J.; Kampert, E.; Wolf-Fabris, F.; Philipp, P.; Bischoff, L.; Voelskow, M.; Mücklich, A.; Schmidt, B.; Skorupa, M.; Helm, M.; Wosnitza, J.;
  • Lecture (Conference)
    11th European Conference on Applied Superconductivity - EUCAS 2013, 15.-19.09.2013, Genua, Italy

Publ.-Id: 19298 - Permalink

Kolorimetrischer Nachweis mittels S-Layer modifizierter Goldnanopartikel
Lakatos, M.; Matys, S.; Pompe, W.; Mertig, M.;
Vorgestellt wird eine einfache und schnelle kolorimetrische und UV/VIS spektroskopische Methode für den Nachweis metallischer Ionen bzw. Ionenkomplexe in wässriger Lösung. Dieses Verfahren basiert auf der Aggregation S-Layer funktionalisierter Goldnanopartikel in Gegenwart einer zu detektierenden Zielspezies. Dabei kommt es aufgrund der Kopplung der Plasmonen zu spektralen Verschiebungen im sichtbaren Bereich des optischen Spektrums. Diese Änderungen können mit dem bloßen Auge durch den Farbumschlag der Lösung von rot nach blau verfolgt werden. Am Beispiel von Arsen(V) und der Funktionalisierung sphärischer Goldnanopartikel mit Oligomerstrukturen des Lysinibacillus sphaericus JG-A12 soll das Potential dieses Nachweissystems aufgezeigt werden. In Kombination mit photometrischen Untersuchungen und einer nachfolgenden Signalauswertung lassen sich auf diese Weise Konzentrationswerte für Arsen(V) unterhalb der von der Europäischen Union geforderten Grenzwerte für Arsen im Trinkwasser (~10 ppb) nachweisen.
Keywords: kolorimetrischer Nachweis, Arsen, Goldnanopartikel, S-Layer
  • Poster
    11. Dresdner Sensorsymposium 2013, 09.-11.12.2013, Dresden, Deutschland
  • Contribution to proceedings
    11. Sensor Symposium, 09.-11.12.2013, Dresden, Deutschland
    DOI: 10.5162/11dss2013/A6

Publ.-Id: 19297 - Permalink

Bubble dynamics in a 3-D gas-solid fluidized bed using ultrafast electron beam X-ray tomography and two-fluid model
Verma, V.; Padding, J. T.; Deen, N. G.; Kuipers, J. A. M.; Bieberle, M.; Barthel, F.; Wagner, M.; Hampel, U.;
Bubble characteristics in a 3-D gas-fluidized bed have been measured using noninvasive ultrafast electron beam X-ray tomography. The measurements are compared with predictions by a two-fluid model based on kinetic theory of granular flow. The effect of bed material (glass, alumina and LLDPE, dp ~1mm), inlet gas velocity and initial particle bed height on the bubble behavior is investigated in a cylindrical column of 0.1m diameter. The bubble rise velocity is determined by cross correlation of images from dual horizontal planes. The bubble characteristics depend highly upon the particle collisional properties. The bubble sizes obtained from experiments and simulations show good agreement. The LLDPE particles show high gas hold-up and higher bubble rise velocity than predicted on basis of literature correlations.
The bed expansion is relatively high for LLDPE particles. The X-ray tomography and two-fluid model results provide in-depth understanding of bubble behavior in fluidized beds containing different granular
material types.
Keywords: Fluidized bed; X-ray tomography; two-fluid model; bubbles

Publ.-Id: 19295 - Permalink

Impact of Eu(III) on mammalian cells as a function of its speciation
Sachs, S.; Heller, A.; Geipel, G.; Bernhard, G.;
In the case of the accidental release of long-lived radionuclides, e.g., actinides, into the environment, knowledge of their behavior in bio-systems is necessary to asses and to prevent radiological and chemical induced adverse health effects. This includes knowledge of the bioavailability and chemo-/radiotoxicity of these elements for/onto cells, which are governed to a large extent by their speciation [1,2]. In order to gain a better process understanding, we study the interaction of trivalent actinides/lanthanides with mammalian cells on a cellular level combining biochemical and analytical methods. Results of these studies can contribute to the estimation of low dose effects and the development of new decontamination strategies.
The cellular tolerance of FaDu cells (human squamous cell carcinoma cell line) toward Eu(III) as an analog for trivalent actinides as well as its uptake into the cells has been studied as a function of the Eu(III) concentration and nutrient composition. To differentiate between chemotoxic and radiotoxic effects of Eu(III), 152Eu (β-, ε) was applied as radioactive tracer besides europium with natural isotope composition. The Eu(III) speciation in the cell culture media has been investigated by time-resolved laser-induced fluorescence spectroscopy as well as by solubility studies in combination with ultrafiltration, ultracentrifugation, cation and anion analysis. These results are used to correlate cytotoxicity and uptake of Eu(III) on/into the cells with its chemical speciation in the nutrient. Presently, we are studying the interaction of Eu(III) with NRK-52E cells (rat kidney epithelial-like cells). The results of these studies will be discussed and compared to those obtained with FaDu cells.
From the studies with FaDu cells it was concluded that the Eu(III) cytotoxicity onto these cells depends on the Eu(III) concentration and is influenced by its chemical speciation. This was also reported, for instance, for the toxicity of U(VI) onto rat kidney cells [3]. In the presence of fetal bovine serum (FBS) as nutrient component, Eu(III) is stabilized in solution by complexation with serum proteins as strong complexing agents and shows a low cytotoxicity. In contrast to that, in the absence of FBS, Eu(III) forms hardly soluble species that are dominated by phosphate ligands. In this binding form, Eu(III) exerts a significantly higher cytotoxicity. The presence of an excess of citrate, as strong complexing ligand, influences the Eu(III) speciation and decreases its toxicity in the absence of FBS. Independent of its speciation, Eu(III) seems to be predominantly bound to the cell surface and does not significantly enter the cells. Under the applied experimental conditions, the tolerance of FaDu cells versus Eu(III) appears to be not significantly influenced by the presence of 152Eu, indicating no additional radiotoxic effect.

[1] Ansoborlo, E. et al., Biochimie 88, 1605 (2008).
[2] Bresson, C. et al., J. Anal. At. Spectrom. 26, 593 (2011).
[3] Carrière, M. et al., Chem. Res. Toxicol. 17, 446 (2004).
Keywords: mammalian cells, europium, interaction, speciation, cytotoxicity, uptake, radiotoxicity, chemotoxicity
  • Contribution to proceedings
    International Conference on Radioecology and Environmental Radioactivity ICRER, 07.-12.09.2014, Barcelona, Spain
  • Lecture (Conference)
    International Conference on Radioecology and Environmental Radioactivity ICRER, 07.-12.09.2014, Barcelona, Spain

Publ.-Id: 19294 - Permalink

Super-radiant THz sources: 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 ranging from atomic physics, condensed matter to biophysics will be discussed.

[1]G.L. Carr et. al., High power terahertz radiation from relativistic electrons,Nature420(2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol.51(2008), 423.
[3]U. Fruehling, 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 Lightsources,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.(2011), 141117.
Keywords: THz control of matter, ultra-fast phenomena, high field driven processes
  • Invited lecture (Conferences)
    Seminar of the Department of Physics and Photon Science at the Gwangju Institute of Science and Technology (GIST), 27.09.2013, Gwangju, South Korea

Publ.-Id: 19293 - Permalink

Super-radiant THz sources: 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 ranging from atomic physics, condensed matter to biophysics will be discussed.

[1]G.L. Carr et. al., High power terahertz radiation from relativistic electrons,Nature420(2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol.51(2008), 423.
[3]U. Fruehling, 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 Lightsources,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.(2011), 141117.
Keywords: super-radiant THz, ultra-fast phenomena
  • Invited lecture (Conferences)
    Seminar of the Center for Quantum-beam-based Radiation Research, KAERI, 25.09.2013, Daejeon, South Korea

Publ.-Id: 19292 - Permalink

Super-radiant THz sources: 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 ranging from atomic physics, condensed matter to biophysics will be discussed.

[1]G.L. Carr et. al., High power terahertz radiation from relativistic electrons,Nature420(2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol.51(2008), 423.
[3]U. Fruehling, 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 Lightsources,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.(2011), 141117.
Keywords: super-radiant THz, ultra-fast phenomena
  • Invited lecture (Conferences)
    Seminar of the Pohang Accelerator Laboratory (PAL), 24.09.2013, Pohang, South Korea

Publ.-Id: 19291 - Permalink

Conceptual Design of Pressure Tube Light Water Reactor with Variable Moderator Control
Rachamin, R.;
An innovative light water reactor concept, which holds a great promise of improving the fuel utilization, has emerged recently based on an idea of the “breed & burn” mode of operation. The novel concept, named PTVM LWR, is a pressure tube type reactor of similar design to ACR-1000, but differing in two aspects. First, the inter-fuel channels spacing, surrounded by the calandria tank, contains a low pressure gas instead of heavy water moderator. Second, the fuel channel design features an additional/external tube (designated as moderator tube) connected to a separate moderator management system. The moderator management system is designed to vary the moderator tube content from “dry” (gas) to “flooded” (light water filled). The moderator variation results in a neutron spectral shift, which allows the implementation of the “breed & burn” mode of operation. In this talk, the novel reactor core design and the physical principles underlying its operation will be described and discussed. Finally, possible research lines for future investigation and continuous design developments will be discussed.
Keywords: pressure tube reactor, “breed & burn”, moderator variation, H/HM ratio, reactivity control
  • Lecture (others)
    R&D Seminar, AECL Chalk River Laboratories, 22.10.2013, Chalk River, Ontario, Canada
  • Lecture (others)
    R&D Seminar, Candu Energy Inc., 24.10.2013, Mississauga, Ontario, Canada
  • Lecture (others)
    R&D Seminar, University of Ontario Institute of Technology, 25.10.2013, Oshawa, Ontario, Canada

Publ.-Id: 19290 - Permalink

Tissue transglutaminase: an emerging target for therapy and imaging
Pietsch, M.; Wodtke, R.; Pietzsch, J.; Löser, R.;
Tissue transglutaminase (transglutaminase 2) is a multifunctional enzyme with many interesting properties resulting in versatile roles in both physiology and pathophysiology. Herein, the particular involvement of the enzyme in human diseases will be outlined with special emphasis on its role in cancer and in tissue interactions with biomaterials. Despite recent progress in unraveling the different cellular functions of transglutaminase 2, several questions remain. Transglutaminase 2 features in both confirmed and some still ambiguous roles within pathological conditions, raising interest in developing inhibitors and imaging probes which target this enzyme. One important prerequisite for identifying and characterizing such molecular tools are reliable assay methods to measure the enzymatic activity. This digest article will provide clarification about the various assay methods described to date, accompanied by a discussion of recent progress in the development of inhibitors and imaging probes targeting transglutaminase 2.
Keywords: Tissue transglutaminase (TGase 2); Cancer; Biomaterial-tissue interface; Activity assays; Inhibitors; Imaging probes

Publ.-Id: 19289 - Permalink

Resource Technology 'Made in Germany' Helmholtz Institute Freiberg for Resource Technologies
Birtel, S.;
the oral contribution gives an overview about the structure of the HIF, its tasks, infrastructure an research topics
Keywords: resource technologies, geometallurgy
  • Invited lecture (Conferences)
    Deutsch- chilenische Wirtschafttage, 15.-16.10.2013, Santiago de Chile, Chile

Publ.-Id: 19288 - Permalink

Ion Beam Analysis for geosciences
Munnik, F.; Heller, R.; Hanf, D.; Buchriegler, J.; Ziegenrücker, R.; Renno, A. D.; Keywords: IBA, PIXE, scanning nuclear microbeam
  • Lecture (others)
    Seminar Instytut Geologii, Uniwersytet im. Adama Mickiewicza, 08.10.2013, Poznan, Polska

Publ.-Id: 19287 - Permalink

Formation of Se(0) nanoparticles by bacteria
Fischer, S.; Steudtner, R.; Maffert, A.; Vogel, M.; Franzen, C.; Barkleit, A.; Raff, J.;
In the present study we investigated the interaction of selenium with Azospirillum brasilense as well as Bacillus and Lysinibacillus strains from a uranium mining waste pile. The biosynthesis of hardly soluble nanospheric Se(0) was observed for A. brasilense only in the presence of Se(IV) under aerobic conditions. After isolation of the Se(0) from the biomass, the characteristics of the nanoparticles were intensively studied by different techniques, namely HG-AAS, ICP-MS, PCS and SEM-EDX. In summary A. brasilense produced very homogeneous nanospheres with highly negative surface charge and a size of 410 ± 110 nm. The Bacillus and Lysinibacillus strains are able to induce red Se(0) nanoparticles after one day of incubation with Se(IV).
Keywords: Se(0) nanoparticles, Azospirillum brasilense, Bacillus sp., Lysinibacillus sp.
  • Poster
    8th HZDR PhD Seminar, 07.-09.10.2013, Bautzen, Germany

Publ.-Id: 19286 - Permalink

Folgen der Korrosion feuerverzinkter Komponenten im Containment eines Druckwasserreaktors nach einem Kühlmittelverluststörfall
Hoffmann, W.; Kryk, H.;
Bei einem Kühlmittelverluststörfall eines Druckwasserreaktors wird in der Anfangsphase die Freisetzung von Bruchstücken des Isolationsmaterials postuliert, die zu Ablagerungen an den Sumpfansaugsieben führen. Neben diesem physikalischen Vorgang, der durch die Strömungsdynamik beeinflusst wird, laufen im nachfolgenden Sumpfumwälzbetrieb Korrosionsprozesse von verzinkten Einbauten mit unterschiedlicher Intensität ab. Durch strömungsinduzierte Korrosion mit dem borsäurehaltigen Kühlmittel wird der schützende Zinküberzug im Leckstrahlbereich lokal sehr schnell aufgelöst und die sich bildenden Rostprodukte können die Notkühlung durch Einlagerung in die Faserablagerungen bis hin zur Verblockung erheblich stören. Die als Gegenmaßnahme vorgesehene Rückspülung beseitigt zwar dieses Problem. Jedoch werden im weiteren Verlauf durch Korrosion relativ großer verzinkter Flächen im borsäurehaltigen Kühlmittel bei ca. 50 °C im Reaktorsumpf höhere Konzentrationen an gelöstem Zink erreicht. An den durch die Nachzerfallswärme aufgeheizten Brennelementen im Kern des Reaktors können sich Ablagerungen an Hüllrohren bzw. Abstandshaltern bilden, die die Kernkühlung in der Spätphase beeinträchtigen.
Experimente mit Zn-haltigen Borsäurelösungen in einem Batch-Reaktor zeigen, dass dieser Effekt nicht auf einem schnellen Ausdampfen des Wassers an sehr heißen Oberflächen beruht, sondern durch eine Abnahme der Löslichkeit von Zinkborat mit steigender Temperatur verursacht wird, die auch bei niedrigen Aufheizraten zu beobachten ist.
Zur Untersuchung der an einem einzelnen Brennstab auftretenden Effekte wurde eine Laborversuchsanlage mit einem elektrisch beheizten Heizelementmodul (DWR-Hüllrohr) errichtet, bei der die Vorgänge der Zn-Auflösung, Zn-Korrosionsprodukt-Abscheidung und Temperierung durch getrennte Kreisläufe entkoppelt sind. Die elektrische Leistung des Heizelements wurde vergleichbar mit einem Brennstab nach der Schnellabschaltung des Reaktors gewählt und der Temperaturgradient über das Heizelement durch die Flussrate im Ringraum zwischen Heizelement und Glasohr realisiert, wobei die Flächen von Ringraum und Heißkanal eines Brennelements vergleichbar sind. Die Hauptmenge der mobilen partikelförmigen Produkte wird mit einem Filter abgeschieden, während die am Heizelement anhaftenden Abscheidungen nach Demontage zugänglich sind. Die Aufheizbedingungen der Zn-haltigen Lösung beeinflussen nicht nur die Menge der gebildeten festen Zn-Korrosionsprodukte sondern auch deren Art. Dabei können verschiedene Zn-borate entstehen, die sich im Zn:B-Verhältnis, in der Abgabetemperatur und dem Gehalt des Wassers, in den Raman-Spektren und auch in ihrem Wiederauflöseverhalten bei niedrigerer Temperatur unterscheiden.
Keywords: LOCA, PWR, Zn-corrosion, boric acid, deposition of corrosion products
  • Lecture (Conference)
    Zittauer Kraftwerkschemisches Kolloquium 2013, 24.-25.09.2013, Jonsdorf, Deutschland
  • Contribution to proceedings
    Zittauer Kraftwerkschemisches Kolloquium 2013, 24.-25.09.2013, Jonsdorf, Deutschland
    Tagungsband Zittauer Kraftwerkschemisches Kolloquium 2013

Publ.-Id: 19285 - Permalink

Orthogonal IRT Imaging
Franzen, C.; Siedler, G.; Franzen, C.; Vetter, S.;
Like in visual photography the images of infrared-thermographic (IRT) measurements suffer distortion effects. In real measurements outside the laboratory quite often the point of view of the IRT camera is angular to the inspected surface. Thus a photogrammetric digital image processing of the results yielding deformation-true information is indispensable for a correct data interpretation and data use in mapping. Naturally for the montage of large true to scale image plans the rectified quality of all single images is a major requirement. With the help of newly developed optic-thermal markers an automatic image processing with marker matching and rectification of IRT image stacks can be realized. Active IRT is successfully used for damage investigations on mural paintings. But also for the investigation on building history and energetic inspection of buildings and monuments the non destructive and even contactless IRT evolved to a indispensable tool. However, those investigations happen on large objects and require several single IRT inquiries before the object is completely scanned in sufficient resolution. Actually developed software now enables seamless image conjunction of the IRT images by post-treatment and matching. Also, as e.g. in standard routine in active IRT, large image stacks have to be handled in parallel.
  • Contribution to proceedings
    DigitalHeritage2013, 27.10.-01.11.2013, Marseille, France
    Proceedings of the 2013 Digital Heritage Congress; Vol. 1, 978-1-4799-3169-9, 633-636

Publ.-Id: 19284 - Permalink

A tomographic study on the effect of liquid/slurry viscosity in a slurry bubble column
Rabha, S.; Schubert, M.; Hampel, U.;
Slurry bubble column (SBC) reactors find a wide range of application in the chemical process, pharmaceutical and biochemical industries, etc. Over the past decades, various experimental and numerical studies have been done in an attempt to capture the impact of solids in terms of solid concentration and solid particle size on various hydrodynamic propertices1-4. However, still the knowledge about the possible effects of solids on the gas-liquid system is not understood clearly. Due to this lack of clear understanding on the influence of the solid particles, the prediction of the complex flow behavior of gas-liquid-solid flows in slurry bubble column reactor becomes very difficult. In most of numerical investigations5-6, the gas flow behaviour was predicted considering the uniform suspension of the solids in the liquid phase, i.e. the slurry phase was modeled as a single pseudo-homogeneous phase. The assumption of a pseudo-slurry phase may probably be reasonable for smaller particles where particle Reynolds number, ReP, is below 0.3 and stokes law assumption is valid. However, for larger particles, where ReP is higher than 0.3, the effect of the solid phase on the liquid cannot be neglected. Furthermore, all the available correlations for slurry viscosity7-8 consider only the effect of Cs, neglecting the effect of particle size and superficial gas velocity. In the present work, an attempt has been made to study the effect of viscosity in two-phase (air / water + glycerol) system and compared with the apparent (slurry) mixture viscosity in three-phase (air / water +glass particles) system on the hydrodynamic parameters like gas holdup at approximately same viscosities under similar operation conditions.
Keywords: Slurry viscosity, Liquid viscosity, Ultrafast electron beam X-ray tomography
  • Lecture (Conference)
    2013 AIChE Annual Meeting, 03.-08.11.2013, San Francisco, USA

Publ.-Id: 19283 - Permalink

Determination of Atmospheric Mercury and its Deposition in Remote Areas of the Northern and Southern Hemisphere
Franzen, C.;
Mercury (Hg) is a pollutant of global concern. Due to its high vapor pressure Hg is a very mobile element and therefore is evident in all environmental compartments and can be both, intra-hemispherically and interhemispherically dispersed.
In order to understand the global mercury cycle and the anthropogenic impact on it, a large number of research activities have been carried out in recent years. On the one hand mercury species in ambient air have been scope of various studies with the objective to characterize the contemporary mercury fate and behavior in the global atmosphere. On the other hand, historical records of mercury in a variety of archives have been used to estimate human impacts on the biogeochemical cycling of mercury.
The first objective of this study was to contribute information on the worldwide distribution and trend of atmospheric mercury. For this the atmospheric species Total Gaseous Mercury (TGM), Reactive Gaseous Mercury (RGM), Total Particulate Mercury (TPM) and mercury in precipitation have been analyzed in remote areas in both, the Northern and the Southern Hemisphere. In order to ensure the determination of reliable data, the establishment of compliant and reliable sampling and analytical set-ups capable for remote sampling areas was the first milestone for this part of the study.
One other intent of the study was to answer the question under which constraints mercury records in peat bogs and lacustrine sediments reflect atmospheric deposition rates and thus can be used to estimate human impacts on the biogeochemical cycling of mercury. With the atmospheric mercury data obtained, contemporary deposition rates were calculated and compared to existing historical mercury records in ombrothrophic peat bogs and lacustrine sediments to test the reliability of these geochemical archives.
The atmospheric data show that there is a significant diurnal and spatial variability of the different species, mainly controlled by meteorological conditions and biogeochemical processes in soils.
The new data contribute to the the existing small data set from remote areas, especially from the Southern Hemisphere, and are a helpful complementary approach to the few stationary sites established for long period observations. Particularly for the region of South America no baseline measurements in remote areas have been performed before. The results provide basic information about the worldwide distribution and trend in atmospheric mercury dynamics.
The calculated mercury wet deposition of 1.3 – 3.5 μg m−2 a−1 found for the different sampling sites in Patagonia show a much better correlation to the Hg accumulation rate found in the lacustrine sediment and evidence that the uncorrected accumulation rates in the upper part of peat bogs and thus the assumed contemporary atmospheric flux might be overestimated.
  • Doctoral thesis
    Universität Heidelberg, 2013
    169 Seiten

Publ.-Id: 19282 - Permalink

Results of the Literature Research of the Oxidation of Isobutane and Current Works.
Willms, T.; Kryk, H.; Hampel, U.;
Reaction paths of the Isobutane oxidation and main reaction products are summarized to identify processes which are influencing the TBHP yield. 13 levers to improve the selectivity could be identified. Several reaction models of the isobutane oxidation from literature are analyzed concerning the reaction conditions and the elementary chemical reactions used.
Furthermore a first flow chart for the micro reactor design is presented. The results of the first meeting with Linde Engineering are discussed and safety issues are pointed out.
The results of DSC experiments concerning the decomposition of TBHP are presented.
  • Lecture (others)
    Halbjahresmeeting Helmholtz-Energie-Allianz, 21.-23.03.2013, Karlsruhe, Deutschland

Publ.-Id: 19281 - Permalink

The role of the enzyme alpha-amylase in binding of An(III)/Ln(III) by oral ingestion
Barkleit, A.; Heller, A.; Bernhard, G.;
In case of incorporation, radionuclides represent a serious health risk to humans due to their (radio-)toxicity. Thus, the determination of their speciation and transport on a molecular level is crucial for the understanding of the transport, metabolism, deposition and elimination in the human organisms. In case of oral ingestion of contaminated food or radioactive substances the first contact medium in the mouth is the aqueous biofluid saliva which contains inorganic ions (mainly Na+, K+, Ca2+, Cl-, CO32-, PO43-) and numerous biomolecules, mainly proteins. One of the major proteins in saliva is the digestive enzyme α-amylase which catalyzes the hydrolysis of the α-1,4 glycosidic linkages of polysaccharides like starch or glycogen. [1]
In this study the speciation of curium(III) and europium(III) in saliva as the first contact medium at oral incorporation was investigated with time-resolved laser-induced fluorescence spectroscopy (TRLFS). For TRLFS measurements, fresh saliva samples from human sources have been spiked in vitro with Eu(III) or Cm(III). The identification of the dominant species was achieved by a comparison of the spectroscopic data with reference spectra obtained from synthetic saliva and the main single components of the biofluid. In the pH range from 6.8 to 7.4 similar spectra were obtained. With respect to reference data, the spectra indicate the formation of a ternary metal complex containing phosphate and carbonate anions and, in addition, a coordination of organic matter, namely α-amylase, to the central metal cation is suggested.
To get more information about the binding behavior of α-amylase various investigations with Eu(III) as inactive analog for An(III) were carried out with porcine pancreatic α-amylase (PPA) which serves as model system for various α-amylase species. Sorption experiments showed a high affinity of Eu(III) to α-amylase in a wide pH range, namely between pH 4 and 8. The analysis of binding isotherms demonstrated that up to 3 Eu3+ ions are bound to one enzyme molecule. Hence, the Eu3+ ions seem to replace the Ca2+ ions, a well-known mechanism in biological systems. The effect of Eu3+ on enzyme activity was determined with the α-amylase assay method by Bernfeld [2]. Eu3+ shows a strong inhibition effect on the enzyme activity, but in the presence of Ca2+ in excess the enzyme activity remains nearly unaffected. This effect might be useful for the refinement of decontamination strategies.

[1] Edgar, W. M., Saliva: its secretion, composition and functions. British Dental Journal 1992, 172, 305-312
[2] P. Bernfeld, Methods in Enzymology 1955, 149-158
  • Poster
    International Conference on Radioecology and Environmental Radioactivity ICRER, 07.-12.09.2014, Barcelona, Spain

Publ.-Id: 19280 - Permalink

A New PSS for the ELBE Accelerator Facility
Justus, M.; Kösterke, I.; Kraft, S.; Michel, P.; Schramm, U.; Lenk, S.;
The ELBE facility (Electron Linear accelerator with high Brightness and low Emittance) is being upgraded towards a Center for High Power Radiation Sources in conjunction with Terawatt & Petawatt femtosecond lasers. The topological facility expansion and an increased number of radiation sources made a replacement of the former personnel safety system (PSS) necessary. The new system based on failsafe PLCs was designed to fulfil the requirements of radiation protection according to effective law, where it combines both laser and radiation safety for the new laser based particle sources. Conceptual design and general specification was done in-house, while detailed design and installation were carried out in close cooperation with an outside firm.
The article describes architecture, functions and some technical features of the new ELBE PSS. Special focus is on the implementation of IEC 61508 and the project track. The system was integrated in an existing (and mostly running) facility and is liable to third party approval. Operational experience after one year of run-time is also given.
Keywords: ELBE, PSS
  • Open Access LogoContribution to proceedings
    ICALEPCS 2013 - 14th International Conference on Accelerator & Large Experimental Physics Control Systems, 06.-11.10.2013, San Francisco, USA
    ICALEPCS2013: Proceedings of the 14th International Conference on Accelerator & Large Experimental Physics Control Systems, Geneva (Switzerland): JACoW / CERN, 978-3-95450-139-7, 191-194
  • Poster
    ICALEPCS 2013 - 14th International Conference on Accelerator & Large Experimental Physics Control Systems, 06.-11.10.2013, San Francisco, USA

Publ.-Id: 19279 - Permalink

Status of Reactor Design and Analytical Investigations
Willms, T.; Kryk, H.; Hampel, U.;
For the investigation of the isobutane oxidation a micro reactor is planned. For its design, the conversion of isobutane has been calculated as a function of temperature and time by a kinetics found in literature to estimate reaction times. Low temperatures (< 130°C) are leading to high residence times. To realize those high residence times, very low isobutane flows are needed which cannot be realized exactly in the case of a capillary reactor of 10 m (< 1 µl/min). So for low temperatures a 100 m capillary has to be used, whereas for higher temperatures a 10 m capillary is sufficient. The gas - liquid relations of some taylor flows at comparable conditions (10 µl flow rate) - realized by hexane and nitrogen - have been studied.
Furthermore the separation of the most important isobutane oxidation products has been presented. Liquid products (DTBP, acetone, TBHP, t-butanol, methanol, formic acid ) are separated by GC-MS using a StabiloWax Column, gaseous components of the medium (isobutane, carbon dioxide, oxygen etc.) are separated by GC-TCD and GC-MS.
  • Lecture (others)
    Halbjahrestreffen der Helmholtz Energie Allianz., 30.09.-02.10.2013, Bochum, Deutschland

Publ.-Id: 19278 - Permalink

Terahertz-induced effects on excitons in magnetic field
Böttge, C. N.; Breddermann, B.; Schneebeli, L.; Kira, M.; Koch, S. W.; Bhattacharyya, J.; Schneider, H.; Helm, M.;
Terahertz-induced intra-exciton transitions are studied in semiconductor quantum-well systems under the influence of a constant magnetic field. A systematic description is developed to include carrier–carrier interactions, terahertz transitions, and magnetic-field effects to the exciton-correlation dynamics. When a magnetic field is present, the exciton states and energies are changed directly and parametrically via the center-of-mass momentum of excitons. The numerical results show that both effects influence the terahertz spectroscopy. Especially, the transition between 1s- and 2p-exciton states is shown to depend strongly on both magnetic field and center-of-mass momentum.
Keywords: semiconductor quantum well, exciton, terahertz

Publ.-Id: 19277 - Permalink

Sorption von Se(VI) an γ-Al2O3
Hering, D.;
Im Hinblick auf die Wirksamkeit von Barriensystemen potentieller Endlager wurden Sorptionsprozesse von Selenationen an γ-Aluminiumoxid untersucht.
Zunächst wurden Untersuchungen zur Charakterisierung der Mineralphase durch Einsatz von Zeta-Potential-Messungen und Röntgenbeugungsspektroskopie durchgeführt. Dabei wurde bestätigt, dass es sich bei dem eingesetzten Feststoff um eine reine Oxidphase handelt, und es wurde widerlegt, dass es beim Kontakt des Minerals mit Wasser zur Bildung von Hydroxiden kommt. Zusätzlich zu diesen Ergebnissen konnte für das verwendete Oxid ein isoelektrischer Punkt bei pH = 9,5...9,6 ermittelt werden.
Ein weiterer wichtiger Schwerpunkt dieser Arbeit bestand darin, Erkenntnisse zur Sorption von Selenationen am γ-Al2O3 durch die Anwendung von Batch-Experimenten zu gewinnen. Im Zuge dieser Experimente sollte die Abhängigkeit der Sorption vom pH-Wert und der Konzentration der Hintergrundelektrolyten Natriumchlorid und Magnesiumchlorid untersucht werden. Dies geschah durch den Einsatz von Zeta-Potential-Messungen und spektroskopischen Daten, welche über ICP-MS ermittelt wurden. Die Ergebnisse zeigen, dass die Sorption sowohl mit steigendem pH-Wert als auch mit steigender Konzentration der Hintergrundelektrolyten verringert wird. Dabei deuten beide Methoden darauf hin, dass es sich bei den durch Sorptionsprozesse gebildeten Komplexen um outersphärische Komplexe handelt.
Eine äußerst wichtige Frage im Hinblick auf die Immobilisierung der Selenationen durch Sorption war die ihrer Reversibilität. Nur, wenn die Sorption irreversibel verläuft, können austretende Kontaminanten immobilisiert und somit ihre Freisetzung in die Umwelt verhindert werden. Die Ergebnisse der IR Spektroskopie weisen darauf hin, dass die stattfindenden Sorptionsprozesse vorwiegend zu relativ schwach gebundenen Selenationen an der Mineraloberfläche führen. Daraus lässt sich schlussfolgern, dass γ Aluminiumoxid im Hinblick auf die Immobilisierung von radioaktivem Selen-79 im Endlager nur geringe Rückhalteeigenschaften besitzt.
  • Bachelor thesis
    Hochschule Zittau - Görlitz, 2013
    66 Seiten

Publ.-Id: 19276 - Permalink

Geowissenschaftliche Berufsfelder - Als Mineralogin in der Endlagerforschung
Franzen, C.;
Vortrag zu Berufsmöglichkeiten in der Endlagerforschung im Rahmen eines Seminars des Bachelor-Studienganges "Geowissenschaften" an der Universität Heidelberg.
  • Lecture (others)
    Berufsfelder in den Geowissenschaften, 15.07.2013, Heidelberg, Deutschland

Publ.-Id: 19275 - Permalink

Investigation of conditions for zinc particle release and transport in the reactor core
Renger, S.; Kästner, W.; Alt, S.; Seeliger, A.; Fiss, D.; Kryk, H.; Hoffmann, W.;
Background of the experimental and methodical work is a loss-of-coolant accident (LOCA) in a PWR. During a LOCA, the leakage water jet as well as the water in the containment can lead to corrosion of galvanized installations (e.g. grates). That means a change of consistency and chemical properties of the coolant during the sump recirculation operation, in particular an increase of the zinc concentration (Zn ions) and the pH-value. Furthermore, it leads to separation of layer-forming zinc compounds (e.g. zinc borate) at hot spots (fouling at fuel assemblies) and/or the crystallization of zinc corrosion products out of the coolant in hot areas. This in turn causes a decrease of pH-value and consequently an increase of the corrosiveness of the coolant flow. This can come along with a chemical transformation of zinc borate to nearly indissoluble zinc oxide by thermo hydrolysis. Spalling of parts of the coating on the surface of the fuel rods could lead to the release of particles into coolant water flow. In combination with released fibrous insulation material, which can be transported into the reactor containment, containment building sump and connected systems, this process leads to pressure build up at the strainers and the spacers of the fuel assemblies and a reduction of the pump performance. In this case, efficient heat dissipation cannot be guaranteed.
In a joint research project between the Institute of Process Technology, Process Automation and Measuring Technology (IPM) of the University Zittau/Görlitz and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the influence of different boundary conditions like the flow structures in the reactor pressure vessel, temperature distributions and the temperature gradient in the central core regions will be investigated. Therefore a test facility containing a 3x3 heated fuel rod dummy configuration was designed and constructed. The design and development of the test facility was accompanied by pre-test calculations and CFD simulations to get information about local surface and fluid temperatures under different flow conditions.
The paper includes a detailed description of the test facility and applied measuring techniques as well as an overview of all boundary conditions considered in the experiments. Main parts of the paper are the pre-calculation and the CFD simulation for the heat transfer in dependency of flow velocity and heat flux.
The investigations have been supported by the German Federal Ministry of Economy and Technology under grant nos.1501340 and 1501341.
Keywords: reactor safety, loss-of-coolant accident, LOCA, pressurized water reactor, PWR, corrosion, boric acid, zinc borate
  • Lecture (Conference)
    21th International Conference on Nuclear Engineering (ICONE21), 29.07.-02.08.2013, Chengdu, China

Publ.-Id: 19274 - Permalink

Verhalten von Zink-Korrosionsprodukten bei der Durchströmung einer beheizten Brennstabkonfiguration
Alt, S.; Kästner, W.; Renger, S.; Seeliger, A.; Kryk, H.; Hoffmann, W.;
In der Spätphase eines postulierten Kühlmittelverluststörfalles in Druckwasserreaktoren können infolge des Sumpfumwälzbetriebes Korrosionsprozesse an verzinkten Containment-Einbauten, welche mit dem austretenden borsäurehaltigen Kühlwasser in Kontakt kommen, auftreten. Dies bewirkt einen Anstieg der Zinkkonzentration im Kühlmittel. Infolge dieser physikochemischen Prozesse können sich feste Zink-Korrosionsprodukte an Heißstellen im Kühlmittelkreislauf (z.B. im Kern) abscheiden. Im Rahmen eines BMWi-Verbundprojektes (FKZ 1501430 und 1501431) wurde anhand von Experimenten an einer halbtechnischen Versuchsanlage der HS Zittau/Görlitz, bestehend aus einer Strömungsschleife mit einer beheizten Brennstabkonfiguration, und entsprechender chemischer Analysen, welche am HZDR durchgeführt wurden, die Bildung von hochporösen Zinkborat-Korrosionsproduktschichten nachgewiesen, die sich vornehmlich an Hüllrohren und Abstandshaltern ablagern und somit die Thermohydraulik im Kern beeinflussen können.
Keywords: reactor safety, pressurized water reactor, loss-of-coolant accident, LOCA, corrosion, zinc borate
  • Lecture (Conference)
    Zittauer Kraftwerkschemisches Kolloquium, 24.-25.09.2013, Jonsdorf, Deutschland
  • Contribution to proceedings
    Zittauer Kraftwerkschemisches Kolloquium, 24.-25.09.2013, Jonsdorf, Deutschland
    Tagungsband Zittauer Kraftwerkschemisches Kolloquium 2013

Publ.-Id: 19273 - Permalink

Bulk and spatially resolved chemical on-line analytics in mineral-processing – a rocky road to success?
Schaefer, J.; Rudolph, M.; Renno, A. D.;
The manifold and extremely elaborate and energy as well as material consumptive process steps to separate valuable minerals from ores should prepare an ideal breeding ground for sophisticated chemical on-line analytics. Success stories are well known, but not as obvious and frequent as anticipated by scientists and entrepreneurs developing such analytical technologies. Bulk analytical methods dominate the sampling and analysis systems in operation.
Geometallurgy, often defined as the science of adapting mineral processing to mineralogy and microstructure of a particular raw material allowing to improve efficiency with existing technology, uses microanalytical methods with sophisticated spatial resolution as workhorse analytics.
We analyse the causes for this contradictory trend. Using typical mineral processing schemes we define the most promising assignment locations of chemical on-line analysis systems, prospective input of chemical data into up- and downstream control of the raw material as well as for quality control of intermediate and final products. On the other hand we will show how the actual state of the art of mineral processing technology precludes the efficiency of prospective spatially resolved chemical on-line analysis systems.
Keywords: Mineral Processing, On-Line Analytics, Resource Analytics, Resource Technology
  • Invited lecture (Conferences)
    PRORA- Fachtagung Prozessnahe Röntgenanalytik, 21.-22.11.2013, Berlin, Deutschland

Publ.-Id: 19272 - Permalink

Measurements in a downscaled water-mockup and numerical simulations for the DRESDYN large scale precession dynamo experiment
Gundrum, T.; Wustmann, B.; Steglich, C.; Engel, H.; Stefani, F.; Gerbeth, G.; Albrecht, T.; Giesecke, A.; Nore, C.;
Precession has been discussed since long as a complementary energy source of homogeneous dynamo action. We delineate the present status of the preparations of the DRESDYN liquid sodium precession experiment, including numerical simulations, pressure measurements, velocity measurements, torque measurements and power measurements in a down scaled water mockup. Furthermore we give an overview about engineering and constructional aspects for the real sodium experiment.
Keywords: Dynamo, Precession, UDV, Sodium
  • Lecture (Conference)
    International Symposium on Geophysical and Astrophysical Dynamos, 07.-12.07.2013, Ascona, Switzerland

Publ.-Id: 19271 - Permalink

Optimierungspotential für Aufbereitungsprozesse durch Nutzung eines Röntgenfluoreszenzspektrometers mit Full-Field-Detektor zur Vorort-Charakterisierung mineralogischer Proben mit inhomogener Elementverteilung
Schaefer, J.; Scharf, O.; Renno, A. D.; Kühn, A.; Wedell, R.; Langhoff, N.; Groh, M.; Gutzmer, J.;
Im Rahmen des BMBF-geförderten „MEGA-Projektes“ haben sich Partner aus der Montanindustrie, Aufbereitungs-Verfahrenstechnik, dem analytischen Gerä­tebau, der geologisch-mineralogischen Forschung und der Anwendungs­forschung im Bereich optischer Technologien zusammengefunden. Dieses Kon­sortium wird gemeinsam Forschungs- und Entwicklungsaufgaben zu analy­tischen und methodischen Möglichkeiten eines XRF-Mine-Spektrometers evaluieren und direkt auf die Anwendungsfälle in Geologie, Bergbau, Aufbe­reitung und Metallurgie ausrichten. Das Ziel ist eine Optimierung der Wert­schöpfungskette von der Erkundung über die Exploration zur Aufbereitung und Metallurgie. Als erster Schritt erfolgt die Konzeption des XRF-Mine-Spektro­meters als Forschungsgerät, welches optimal an die Lösung ressourcentech­nologischer Fragestellungen angepasst ist.
Das anvisierte XRF-Mine-Spektrometer für die (ultra)schnelle Vorort Röntgen­fluoreszenzspektroskopie (XRF-Spektroskopie) wird ein Analysegerät zur Spurenelementanalyse metallischer und mineralischer Primär- und Sekun­därrohstoffe. Die Bestimmung der Spurenelemente sowie ihrer räumlichen Ver­teilung in verschiedenen Mineralen erfolgt dabei in stark inhomogenen Ma­trices. Dies gestattet neben der Bestimmung von Gesamtspurenelement­gehalten auch die Berechnung aufbereitungstechnologisch relevanter Para­meter wie Korngrößen, Verwachsungsverhältnisse und Liberalisierungsgrad. Anhand verschiedener technologisch relevanter Aufbereitungsschemata von Metallerzen und Industriemineralen wird das Optimierungspotential der ent­sprechenden Aufbereitungsprozesse durch den Einsatz des XRF-Mine-Spec­trometers aufgezeigt.
Keywords: X-Ray Spectrometry, X-Ray Colour Camera, Mineral Processing, Geometallurgy, Resource Analytics
  • Poster
    Aufbereitung und Recycling 2013, 13.-14.11.2013, Freiberg, Deutschland

Publ.-Id: 19270 - Permalink

Ultratrace element analytics at its limits – a valuable tool for geoscientists?
Renno, A.;
Definition of ultratrace elements,
The Universal presence of elements and the Minimum concentration of an element in a mineral phase
Analytical challenges for ultratrace element analysis
The concept of an ideal or unconditioned analysis
The Super-SIMS concept
Geochemistry of ultratrace elements
Keywords: Geochemistry, Ultratrace elements, Super-SIMS
  • Lecture (others)
    Seminar, 08.10.2013, Poznan, Polen

Publ.-Id: 19269 - Permalink

Ultrasonic flow measurements in electrically magnetized Couette-Taylor and related flows
Gundrum, T.; Seilmayer, M.; Pal, J.; Eckert, S.; Stefani, F.; Cramer, A.; Gerbeth, G.;
Studying magnetized Couette-Taylor experiments requires an interaction of the flow and magnetic field. So a good conductive liquid is needed. Therefore liquid metal is the best choice in laboratory experiments. Liquid metals are opaque and optical measurement techniques are not suitable. The Ultrasound Doppler Velocimetry (UDV) is a non-intrusive technique to measure velocities of liquid flows. Because of the ability to work in opaque fluids and to deliver complete velocity profiles in real time it is very attractive for liquid metal applications.
For instance the MRI comes up at magnetic fields which are generated by strong currents up to 20 kA in the modified PROMISE facility. Other related experiments at our multipurpose magnetic field system (MULTIMAG) using alternating magnetic fields to influence or drive the flow. Magnetizing a flow due to electrical current generates always electromagnetic indifferences (EMI) on the weak receiver signal at the UDV instrument.
In this poster we present solutions to reduce EMI and present some special results from the magnetorotational instability (MRI), discovered by Velikhov in 1959 and a wind in a thermal and electromagnetic driven flow.
Keywords: MHD, EMI, PROMISE, UDV, Ultrasonic
  • Poster
    18th International Couette-Taylor Workshop, 24.-26.06.2013, Enschede, The Netherlands

Publ.-Id: 19268 - Permalink

In search for the real value: Freiberg strategy for obtaining reference materials for resource technology microanalysis
Michalak, P.-P.; Renno, A. D.; Merchel, S.; Munnik, F.; Gutzmer, J.; Uecker, R.; Galazka, Z.; Heller, H.-P.; Radtke, M.; Reinholz, U.;
kein Abstract erforderlich
Keywords: reference materials, ion beam analytics
  • Lecture (others)
    Seminar Instytut Geologii, Uniwersytet im. Adama Mickiewicza, 08.10.2013, Poznan, Polska

Publ.-Id: 19267 - Permalink

Radiofluorination and biological evaluation of N-aryl-oxadiazolyl-propionamides as potential radioligands for PET imaging of cannabinoid CB2 receptors
Teodoro, R.; Moldovan, R.-P.; Lueg, C.; Günther, R.; Donat, C. K.; Ludwig, F.-A.; Fischer, S.; Deuther-Conrad, W.; Wünsch, B.; Brust, P.;
The level of expression of cannabinoid receptor type 2 (CB2R) in healthy and diseased brain has not been fully elucidated. Therefore, there is a growing interest to assess the regional expression of CB2R in the brain. Positron emission tomography (PET) is an imaging technique, which allows quantitative monitoring of very low amounts of radiolabelled compounds in living organisms at high temporal and spatial resolution and, thus, has been widely used as a diagnostic tool in nuclear medicine. Here, we report on the radiofluorination of N-aryl-oxadiazolyl-propionamides at two different positions in the lead structure and on the biological evaluation of the potential of the two tracers [18F]1 and [18F]2 as CB2 receptor PET imaging agents.

High binding affinity and specificity towards CB2 receptors of the lead structure remained unaffected by the structural changes such as the insertion of the aliphatic and aromatic fluorine in the selected labelling sites of 1 and 2. Aliphatic and aromatic radiofluorinations were optimized, and [18F]1 and [18F]2 were achieved in radiochemical yields of ≥30% with radiochemical purities of ≥98% and specific activities of 250 to 450 GBq/μmol. Organ distribution studies in female CD1 mice revealed that both radiotracers cross the blood–brain barrier (BBB) but undergo strong peripheral metabolism. At 30 min after injection, unmetabolized [18F]1 and [18F]2 accounted for 60% and 2% as well as 68% and 88% of the total activity in the plasma and brain, respectively. The main radiometabolite of [18F]2 could be identified as the free acid 18F]10, which has no affinity towards the CB1 and CB2 receptors but can cross the BBB.

N-aryl-oxadiazolyl-propionamides can successfully be radiolabelled with 18F at different positions. Fluorine substitution at these positions did not affect affinity and specificity towards CB2R. Despite a promising in vitro behavior, a rather rapid peripheral metabolism of [ 18F]1 and [ 18F]2 in mice and the generation of brain permeable radiometabolites hamper the application of these radiotracers in vivo. However, it is expected that future synthetic modification aiming at a replacement of metabolically susceptible structural elements of [ 18F]1 and [ 18F]2 will help to elucidate the potential of this class of compounds for CB2R PET studies.
Keywords: Blood–brain barrier; Cannabinoid receptors; 18F labelling; Molecular imaging; Positron emission tomography

Publ.-Id: 19265 - Permalink

Using the "good" radionuclides for dating in geo-and cosmochemistry
Merchel, S.; Akhmadaliev, S.; Pavetich, S.; Rugel, G.; Ziegenrücker, R.; DREAMS-Users;
kein Abstract erforderlich
Keywords: AMS, dating, geochronology, geomorphology, cosmochemistry, radionuclides
  • Lecture (others)
    Seminar Instytut Geologii, Wydział Nauk Geograficznych i Geologicznych, Uniwersytet im. Adama Mickiewicza w Poznaniu, 08.10.2013, Poznan, Polska

Publ.-Id: 19263 - Permalink

The 6 MV tandem accelerator and its applications at HZDR
Akhmadaliev, S.; Heller, R.; Munnik, F.; Neelmeijer, C.; Abrasonis, G.; Rugel, G.; Pavetich, S.; Ziegenrücker, R.; Renno, A. D.; Merchel, S.; Kolitsch, A.; von Borany, J.;
The 6 MV tandem accelerator system at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is dedicated for non-destructive spatial- and depth-resolved analysis using ion beam techniques as well as for material modification via high-energy ion implantation and for accelerator mass spectrometry (AMS) [1].
The accelerator is a medium current 6 MV TandetronTM (HVEE) operating at terminal voltages of 0.3 – 6 MV with high energy stability. Originally, the accelerator was equipped with two separate ion injection systems only: a) the multipurpose ion injector (MPI) for ion beam analysis and high-energy ion implantation; b) the bouncer injector with two Cs-sputter ion sources is exclusively used for AMS purposes. For more flexibility an additional injection system including two gas ion sources, one for He and one for 15N ions, is actually under construction.
The AMS system (DREAMS) is applied for measurements of radionuclides like 10Be, 26Al, 36Cl, 41Ca, and 129I with ultimate sen¬sitivity. One of the original AMS ion sources was modified improve AMS performance for 36Cl and 129I measurements.
The existing IBA equipment is used for RBS, ERD (including high resolution ERD), PIXE/PIGE, NRA and IBA with an external proton beam. A newly installed high-speed PIXE system allows to provide fast spatial-resolved measurements using an X-ray camera. The cluster tool system combines surface analysis using IBA methods with thin film deposition and modification techniques in one tool.
High-energy ion implantation or irradiations can be performed at two different end-stations. One of them is equipped with an automatic wafer-handling system allowing irradiation of samples with a size up to 20 cm  20 cm, which is routinely applied for industrial services.
Keywords: Ion accelerator, ion beam analysis, AMS, IBA, ion implantation
  • Poster
    ECAART11 - the 11th European Conference on Accelerators in Applied Research and Technology, 09.-13.09.2013, Namur, Belgien

Publ.-Id: 19262 - Permalink

Microbial influences on radionuclide behaviour – an example of less-understood problems and how to solve them
Moll, H.; Lütke, L.; Cherkouk, A.; Selenska-Pobell, S.; Bernhard, G.; Brendler, V.;
The potential ambivalent effects of microorganisms on radionuclide transport in the near and far -field of nuclear waste repositories up to the biosphere is discussed. Issues such as microbially induced redox processes of radionuclides, the role of se-creted microbial bioligands, of biosorption and biocolloids, the in-situ kinetics of mi-crobial reactions and the quantification of their products are addressed.
Besides the prominent processes influencing the migration of actinides in the envi-ronment, e.g. sorption onto mineral surfaces, there is growing attention to the influ-ence of indigenous microorganisms on actinide speciation. The concept of geological disposal comprises a detailed knowledge concerning potential host rock formations also in terms of such microorganisms. It is well known that respective bacteria can affect the speciation and hence the mobility of actinides. Thus, dominant bacterial strains from sites destined for future nuclear waste deposition have to be investigated regarding their interaction mechanisms with soluble actinide ions. The understanding of the speciation and the structure of the radionuclide complexes formed in presence of indigenous bacteria over a range of geochemical parameters (e.g., pH, metal concentration) becomes indispensable for eventually predicting the safety of a planned nuclear waste repository. The impact of bacteria on radionuclide speciation will be discussed by taking three examples:
a) the influence of the Mont Terri Opalinus Clay isolate Sporomusa sp. on the pluto-nium speciation; b) curium(III) interaction with cells of the Äspö -groundwater bacte-rium Pseudomonas fluorescens; and c) curium(III) complexation/mobilization with pyoverdins secreted by the Äspö -strain P. fluorescens.
Keywords: actinides, bacteria, microbes
  • Lecture (Conference)
    IGD-TP 4th Exchange Forum (EF4), 29.-30.10.2013, Prague, Czech Republic

Publ.-Id: 19261 - Permalink

Synchrotron radiation microtomography of Taylor bubbles in capillary two-phase flow
Boden, S.; Dos Santos Rolo, T.; Baumbach, T.; Hampel, U.;
We report on a study to measure the three-dimensional shape of Taylor bubbles in capillaries using synchrotron radiation in conjunction with ultrafast radiographic imaging. Moving Taylor bubbles in 2 mm round and square capillaries were radiographically scanned with an ultrahigh frame rate of up to 36,000 fps and 5.6 μm pixel separation. Consecutive images were properly processed to yield 2D transmission radiographs of high contrast-to-noise ratio. Application of 3D tomographic image reconstruction disclosed the 3D bubble shape. The results provide a reference data base for development of sophisticated interface resolving CFD computations.
Keywords: Taylor bubble, synchrotron X-ray micro-tomography, two-phase flow

Publ.-Id: 19260 - Permalink

In-situ ion beam irradiation: X-ray scattering & diffraction experiments
Roshchupkina, O. D.; Baehtz, C.; Facsko, S.; Bischoff, L.; Posselt, M.; Grenzer, J.;
Ion beam techniques are widely used in semiconductor and thin film industry for introducing dopant atoms into materials. Ion implantation is characterized by fast dynamic processes related to the formation and relaxation of collision cascades (100fs – 100ps), finally leading to the formation of different types of defects (vacancies, self-interstitials, clusters, etc.). The material undergoes also other strong modifications. For instance, implantation leads to a strained layer which expands in the direction normal to the substrate surface. This is due to the point that the bulk material prevents any lateral macroscopic expansion; and as a result the thin irradiated layer is subjected to an in-plane biaxial compressive stress due to the continuous accumulation of defects. Unfortunately, ion irradiation is a very fast process and it is almost impossible to monitor it in-situ with the present x-ray sources. However, the accumulation of damage and the diffusion of defects and implanted species are much slower process and can be observed in-situ using a time resolution in the order of seconds.
An in-situ ion beam implantation experiment was set up at ROBL/MRH at ESRF. For this purpose an ion gas source with a maximal acceleration voltage of 5keV was mounted on a sputtering chamber. To realize sufficient volume damage the ion energy was further raised by increasing the electrostatic potential of the irradiated sample to 20keV using an additional power supply. Si and Al2O3 (001)-oriented substrates were irradiated using He+ at an ion flux of about 10^{13}ions/cm^{2}s at room temperature. Reciprocal space maps were measured to study the evolution of the implanted layer.
Keywords: In-situ ion beam implantation
  • Lecture (Conference)
    9th Autumn School on X-ray Scattering from Surfaces and Thin Layers, 25.-28.09.2013, Smolenice, Slovakia

Publ.-Id: 19259 - Permalink

Contactless Flow Rate Sensor for Heavy Liquid Metals
Buchenau, D.; Eckert, S.; Gerbeth, G.; Priede, J.; Lenk, S.;
Control of the flow rate of liquid metals is required in a number of technological processes such as the cooling of liquid metal cooled nuclear reactors, transmutation systems and the dosing and casting of liquid metals. Electromagnetic flow meters play an important role in the diagnostics and automatic control of such processes in order to measure the integral flow rate in arbitrary pipes and channels with electrically conducting and non-conducting walls. A number of different electromagnetic flow meter designs have been developed starting from the end of the forties of the last century.
Commercial electromagnetic flow meters are typically based on the flow-induced electrical voltage measurements by electrodes in direct contact to the melt in a steady magnetic field. In view of the typical problems coming along with applications at liquid metal flows such as high temperatures, interfacial effects and corrosion, the main disadvantage of this type of flow meter is the electrical contact to the liquid metal, which is necessary to measure the electric potential difference. Therefore, contactless operating measurement techniques are very attractive for liquid metal applications. Such flow rate sensors are based on the flow-induced disturbance of an externally applied AC or DC magnetic field which manifests itself in modified amplitudes of the field, in a modified phase distribution of the field or in a force or momentum exerted on the source of the magnetic field. This work deals with the development of new concepts for contactless operating measurement techniques. A first commercially available prototype will be presented.
Keywords: Electromagnetic flow meter, Sensitivity, Measurement uncertainty, Sensor calibration, Liquid metal coolants
  • Lecture (Conference)
    Fourth Conference of Heavy Liquid Metal Coolants in Nuclear Technologies, 23.-27.09.2013, Obninsk, Russia

Publ.-Id: 19258 - Permalink

New Velocity Measuring Techniques for Liquid Lead and LBE Flows
Buchenau, D.; Eckert, S.; Gerbeth, G.; Stefani, F.; Wondrak, T.;
Liquid metal cooling or liquid metal targets belong to innovative reactor concepts such as fast reactor cooled by sodium or lead and the lead-bismuth target in a transmutation system. The safe and reliable operation of liquid metal systems requires corresponding measuring systems and control units, both for the liquid metal single-phase flow as well as for bubble-laden liquid metal two-phase flows. However, velocity measurements in opaque liquid metal flows still represent a challenging task as commercial measuring systems are not available for such fluids. During the last 15 years, considerable effort was spent at HZDR on the development and qualification of techniques to measure the velocity in metallic melts. Especially, significant progress has been achieved in the field of non-invasive measuring techniques. Recent reviews regarding the principles of different velocity measurement systems and their applicability have been published.
In general, measurement techniques are needed to determine flow rates, flow velocities, heat fluxes, pressures, and free surface levels. Within this paper we present some new developments comprising electromagnetic flow meters, ultrasonic Doppler measurements and a contactless inductive flow tomography. The capabilities of these measuring techniques have been verified by tests at HZDR using various liquid metal loops operating with lead, LBE, SnBi or sodium.
Keywords: Flow measurements, Liquid metal coolants, Electromagnetic flow meter, Ultrasound Doppler velocimetry, Contactless inductive flow tomography, X-ray radisocopy
  • Lecture (Conference)
    Fourth Conference of Heavy Liquid Metal Coolants in Nuclear Technologies, 23.-27.09.2013, Obninsk, Russia

Publ.-Id: 19257 - Permalink

Photodisintegration studies of astrophysically relevant p-nuclei
Nair, C. K.;
The majority of the light elements up to iron (Fe) are formed by successive rounds of thermonuclear fusion burning in the stellar interiors. The nuclei heavier than iron (Z>26) are being synthesized mainly by neutron-capture reactions - the astrophysical r-and s-processes. There are 35 neutron deficient stable isotopes between Se and Hg which are shielded from the rapid neutron capture by stable isobars. These so-called p-nuclei are produced in explosive stellar environments via photodisintegration reactions like (γ,n), (γ,p) and (γ,α) on r- or s-seed nuclei. The reaction rates of the p-nuclei are mostly based on theoretical parameterizations using statistical model calculations. At the bremsstrahlung facility of the superconducting electron accelerator ELBE, photon-induced reactions of the p-nuclei are being studied.
In the scope of this thesis work, photodisintegration measurements of the p-nuclei 92Mo and 144Sm have been performed via the photoactivation technique. The residual nuclei resulting from photoactivation were studied via γ-ray spectroscopy. For the decay measurements of short-lived nuclei, a pneumatic delivery system has been used. In the case of 144Sm(°,p) and 144Sm(γ,α) reactions, the activated samarium samples with very low counting statistics were measured at the underground laboratory "Felsenkeller" in Dresden. The experimental activation yields for the 144Sm (γ,n), (γ,p) and (γ, α) and the 92Mo(γ,α) reactions were determined. It is to be emphasized that the (γ,p) and (γ,α) reactions were measured for the first time in a laboratory at astrophysically relevant energies.
In all the mentioned experiments, special care was taken to determine the endpoint energy of the bremsstrahlung spectra by using the photodisintegration of deuteron. The 197Au(γ,n)196Au reaction has been established as an activation standard. The photoactivation yields for the 197Au(γ,n) and 144Sm(γ,n) reactions have been compared to the yield calculated using cross sections from previous photoneutron experiments. A comparison of the two data sets leads to a conclusion on the inaccuracies in previous data. The statistical uncertainties involved in the activation experiments are very small except for the case of decay spectra with weak counting statistics. The systematic uncertainties are mostly from the experimental determination of photon flux. A detailed discussion of the overall uncertainty is provided.
Hauser-Feshbach statistical model calculations using TALYS and NON-SMOKER codes have been performed for all the concerned reactions. The experimental activation yields, in general, agree within a factor of 2 to the simulated yields using statistical model predictions. The sensitivity of the model codes to the nuclear physics inputs like optical-model potentials, nuclear level densities and γ-ray strength functions has been tested.
Keywords: Photodisintegration, p-nuclei
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-039 2013
    ISSN: 2191-8708


Publ.-Id: 19256 - Permalink

Photoaktivierung des p-Kerns Mo-92 am Bremsstrahlungsmessplatz von ELBE
Erhard, M. A.;
Die kosmische Nukleosynthese 35 protonenreicher stabiler Nuklide zwischen Selen und Blei kann nicht durch Neutroneneinfangprozesse erklärt werden. Es wird angenommen, dass diese Kerne in explosiven Szenarien, wie Supernova-Explosionen durch Protoneneinfang oder Photodesintegrationsprozesse, erzeugt werden, jedoch sind die solaren Häufigkeiten dieser sogenannten p-Kerne noch nicht verstanden. Der p-Kern mit der größten Isotopenhäufigkeit, 92Mo, wird in Nukleosynthese-Netzwerkrechnungen deutlich unterproduziert.
Eine mögliche Ursache könnten unpräzise Reaktionswirkungsquerschnitte sein, da die meisten Wirkungsquerschnitte nur aus Modellrechnungen bekannt sind. Daher war es naheliegend, die Photodesintegrationswirkungsquerschnitte von 92Mo mit der Methode der Photoaktivierung an der Strahlungsquelle ELBE im Forschungszentrum Dresden-Rossendorf zu überprüfen.
Durch die hohe Intensität der Bremsstrahlung von bis zu 10^9 MeV^-1cm^-2s^-1 im Energiebereich bis zu 20 MeV konnten im Rahmen dieser Arbeit erstmals nicht nur die (γ,n)-, sondern auch die (γ,p)-Reaktionen an 92Mo bei astrophysikalisch relevanten Energien untersucht werden. Durch die Messungen an zwei Bestrahlungsplätzen konnten systematische Unsicherheiten reduziert werden. Insbesondere wurde eine präzise Bestimmung der Photonenfluenz vorgenommen: Am Kernphysikmessplatz erfolgte die Bestimmung mittels Kernresonanzfluoreszenz an 11B. Im Elektronenstrahlfänger wurde die Photodesintegrationsreaktion 197Au(γ,n) zur Normierung der Photonenfluenz verwendet, nachdem sie zuvor am Kernphysikmessplatz überprüft wurde.
Die Reaktion 92Mo(γ,n)91mMo, mit einer Halbwertszeit des Endkerns von 65 s, war dank einer Rohrpost zugänglich, mit der die Proben in weniger als 10 s von der Bestrahlungsstation zum Zerfallsmessplatz transportiert werden können. Die Messungen dieser Arbeit bestätigen im wesentlichen die Hauser-Feshbach-Modellrechnungen bezüglich der Photodesintegrationsreaktionen (γ,n) und (γ,p). Die Unterproduktion der Mo- und Ru-Isotope ist daher nicht erklärbar durch ungenaue Wirkungsquerschnitte. Zur Nukleosynthese dieser Kerne müssen andere astrophysikalische Prozesse, z.B. neutrinoinduzierte Reaktionen beitragen.
Die gemessenen Photoaktivierungsausbeuten haben eine hohe Empfindlichkeit auf die Photonenstärkefunktion. ÄAnderungen der Dipolriesenresonanzparameter wirken sich stärker auf berechnete Ausbeuten aus, als ÄAnderungen der Kernniveaudichte oder der Parameter des optischen Modells. Durch gleichzeitige Messung der Photodesintegration am Kern 100Mo konnten Unsicherheiten in der Normierung von Photoneutronenexperimentdaten aus der Positronenannihilation im Flug geklärt werden.
Keywords: photoactivation, photodisintegration, bremsstrahlung, p-process, p-nucleus, Mo-92, Mo-100, Au-197, B-11, ELBE, NRF, HPGe, deuteron break-up, pneumatic delivery, Hauser-Feshbach, TALYS
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-038 2013
    ISSN: 2191-8708


Publ.-Id: 19255 - Permalink

In-situ vibrational spectroscopic identification of Np(V) sorption complexes at the mineral oxide-water interface
Müller, K.; Berger, J.; Gröschel, A.;
Neptunium (Np) is one of the most important components of nuclear waste to consider for the long-term safety assessment of nuclear waste repositories, due to the increasing enrichment, the long half-life and the high toxicity of Np-237. Hence, great attention is attracted to its geochemistry [1]. Among the various geochemical reactions, the molecular processes occurring at the solid-water interface, e.g. sorption onto mineral phases, surface precipitation, and colloid formation strongly affect the migration behavior of the radioactive contaminant in the environment [2]. Thus, various components of geological materials, such as iron oxides and hydroxides play an important role in regulating the mobility of actinides in aquifers, due to their widespread environmental presence, high sorption capacity and tendency to form coatings on mineral surfaces [3]. In recent years, the sorption behavior of Np(V), the most relevant oxidation state under ambient conditions, onto iron oxides was mainly studied by macroscopic experiments [4]. For a better understanding of the molecular events occurring at the mineral’s surfaces, ATR FT-IR spectroscopy is a useful tool for the in-situ identification of surface species [5]. In addition, time-resolved measurements provide kinetic information on the surface reactions.
In this work, Np(V) sorption on the oxyhydroxides of Fe, Mn, Si and Ti is investigated by in-situ ATR FT-IR spectroscopy under a variety of environmentally relevant sorption conditions. Upon sorption of micromolar Np(V) on Fe2O3, a band observed at 789 cm−1 is assigned to the antisymmetric stretching vibrational mode (ν3) of the neptunyl ion (Fig.1). The IR spectrum obtained at equal conditions in an aqueous solution shows the absorption of ν3(NpVO2) at 818 cm−1 [5]. The red shift of ν3 to 789 cm−1 upon sorption can be assigned to an inner-sphere sorption complex. Kinetic experiments have shown that only one sorption complex was formed independent from Np(V) loading. Furthermore, no impact of ionic strength (1- 10-4 M NaCl) and pH (≤ 10) on the sorbed species was found. From a comparison of Np(V) surface complexation on different mineral oxides, namely Si, Mn, Fe and Ti oxides, a very similar sorption behavior was elucidated.

Fig. 1: ATR FT-IR spectra of the sorption complexes formed onto several mineral oxides (50 µM Np(V), 0.1 M NaCl, pH 7, 60 min sorption, 0.1 mg mineral oxide/cm2, N2).

[1] Kaszuba, J.P. et al. (1999) Environ. Sci. Technol. 33, 4427-4433.
[2] O'Day, P.A. (1999) Rev. Geophys. 37, 249-274.
[3] Tochiyama, O. et al. (1996) Radiochim. Acta 73, 191-198.
[4] Brendler, V. et al. (2003) 61, 281-291.
[5] Müller, K. et al. (2009) Environ. Sci. Techn. 43, 7665-7670.
  • Invited lecture (Conferences)
    Spring 2014 National ACS meeting EOC division session “Geochemical Processes at Mineral-Water Interfaces: From Atomic-Scale Observations to Field-Scale Phenomena”., 16.-20.03.2014, Dallas, USA

Publ.-Id: 19254 - Permalink

Transverse emittance measurement by slit-scan method for an srf photo injector
Lu, P.; Arnold, A.; Vennekate, H.; Michel, P.; Murcek, P.; Teichert, J.; Xiang, R.;
New measurements of the transverse emittance for a Superconducting Radio Frequency (SRF) gun are conducted with slit-scan method. This contribution introduces the experimental setup, a detailed algorithm and first measurement results. The algorithm proves effective of handling irregular images while the phase space measurement is performed with high resolution. The measured values are around 1-2 πmm•mrad. The results are compared with ASTRA simulations and quad-scan measurement, followed with analysis about the measurement accuracy.
Keywords: SRF-gun, emittance measurement, slit-scan
  • Open Access LogoContribution to proceedings
    FEL2013 - 35th international Free-Electron Laser Conference, 26.-30.08.2013, New York, USA

Publ.-Id: 19253 - Permalink

Emittance Compensation for an SRF Photo Injector
Vennekate, H.; Arnold, A.; Kneisel, P.; Lu, P.; Murcek, P.; Teichert, J.; Will, I.; Xiang, R.;
Many future electron accelerator projects such as energy recovery linacs (ERLs), high power free electron lasers (FELs) and also some of the new collider designs rely on the development of particle sources which provide them with high average beam currents at high repetition rates, while maintaining a low emittance. Superconducting radio frequency (SRF) photo injectors represent a promising concept to give just that, offering the option of a continuous wave (CW) operation with high bunch charges. Nevertheless, emittance compensation for these electron guns, with the goal of reaching the same level as normal conducting sources, is an ongoing challenge. This paper is going to discuss several approaches for the 3-1/2-cell SRF gun installed at the accelerator facility ELBE at the Helmholtz Center Dresden-Rossendorf including the installation of a superconducting solenoid within the injector’s cryostat and present the currently used method to determine the beam’s phase space.
Keywords: SRF Gun, Emittance, ERL, FEL
  • Open Access LogoContribution to proceedings
    SRF 2013 - 16th International conference on RF Superconductivity, 23.-27.09.2013, Paris, France
    Proceedings of SRF 2013
  • Poster
    SRF 2013 - 16th International conference on RF Superconductivity, 23.-27.09.2013, Paris, France


Publ.-Id: 19252 - Permalink

Annual Report 2010 - Institute of Safety Research
Gerbeth, G.; Schäfer, F.; (Editors)
The Institute of Safety Research (ISR) was over the past 20 years one of the six Research Institutes of Forschungszentrum Dresden-Rossendorf e.V. (FZD), which in 2010 belonged to the Wissenschaftsgemeinschaft Gottfried Wilhelm Leibniz. Together with the Institutes of Radiochemistry and Radiation Physics, ISR implements the research programme „Nuclear Safety Research“ (NSR), which was during last years one of the three scientific programmes of FZD. NSR involves two main topics, i.e. “Safety Research for Radioactive Waste Disposal” and “Safety Research for Nuclear Reactors”. The research of ISR aims at assessing and enhancing the safety of current and future reactors, the development of advanced simulation tools including their validation against experimental data, and the development of the appropriate measuring techniques for multi-phase flows and liquid metals.
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-004 2011
    ISSN: 2191-8708


Publ.-Id: 19251 - Permalink

Investigation of Gas Bubble Velocities from Experimental Data of Ultrafast two-layer electron beam X-ray Tomography
Patmonoaji, A.; Banowski, M.; Lucas, D.; Deendarlianto;
While for measurements in diluted two-phase flows optical methods are frequently applied there is a clear demand for measurement systems for dense two-phase flows. Measurement systems which have the capability to measure flow condition in high accuracy and high detail is needed for understanding the physical mechanism of flow phenomena and also especially for improvement and validation of new two phase flow simulation code model.
At the Fluid Dynamics Institute at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a unique ultrafast X-ray tomography named ROFEX (Rossendorf fast electron beam X-ray tomography) was developed. This non-intrusive measurement technique with high spatial and temporal resolution; enables to measure gas liquid phase distribution in detail and high accuracy. A frame rate up to 8000 Hz for simultaneous dual plane measurement and a spatial resolution of 2 mm can be reached. Large range of combination of gas-liquid velocities can be measured without any disturbance.
ROFEX works according to scanned electron beam principle. An electron beam is aimed to a circular metallic target using focusing and deflecting system. Hence rotating X-ray fan that radiates the flow in circular pattern is generated. A detector ring is employed to capture the attenuation value of the X-ray intensity. Further processing with filtered back-projection, reconstructed data result in the form of 3D gray value array. This array is processed with special bubble segmentation algorithm which results in bubble parameters such as bubble volume, detected position and detected time are able to be obtained at the end of this process.
Presently the gas bubble velocities are determined by a cross-correlation from dual measurement planes data which results in radial averaged gas velocity profiles. In this work a new improved method which has capability to derive velocities of single gas bubble inside the flow has been developed. The new method works by pairing the correct bubbles that are detected at both measurement planes. In order to acquire the correct bubbles pair, comparison of bubble parameters for instance volume, detected position and detected time are used. Therefore probability functions are defined for each parameter. If the correct bubbles pair is found, the difference of bubble time shift between both measurement planes can be determined. Therefore, gas bubble velocity is obtained by dividing the measurement plane distance with difference of bubble time detection.
In this paper, detailed explanation of the algorithm working principle is given. The algorithm was tested for wide range of flow characteristic and was validated using phantom measurement data. Radial average velocity obtained by this method was also compared with the result from cross-correlation. Velocity field result for wide range of flow structure was also created for further understanding of gas bubbles movement physical mechanism.
This work is carried out in the frame of a current research project funded by the German Federal Ministry of Economics and Technology, project number 150 1411.
Keywords: X-ray, Computed Tomography, Gas-Liquid Flow, Gas Bubble Velocities, Flow Measurement
  • Lecture (Conference)
    12th Annual National Seminar on Mechanical Engineering, 23.-24.10.2013, Bandar Lampung, Indonesia
  • Contribution to proceedings
    12th Annual National Seminar on Mechanical Engineering, 23.-24.10.2013, Bandar Lampung, Indonesia

Publ.-Id: 19250 - Permalink

Harnessing laser plasma accelerators for radiation therapy - Lab status and recent results from Dresden
Schramm, U.;
Demanding applications like radiation therpy of cancer have pushed the development of laser plasma proton accelerators and defined novel levels of control and monitoring capabilities in experiments. In this presentation the status of the joint activities of the Dresden groups at HZDR running the high power laser Draco and at Oncoray, the national center for radiation research in oncology, will be briefly summarized. Emphasis will be given to the energy scaling of proton bunches accelerated in the TNSA regime with and during ultra-short pulses, potential instabilities in the process, methods for online monitoring, and to the status of the ongoing upgrade of Draco to PW power level. The presentation will be complemented by a demonstration of the simulation capabilities of PIConGPU especially with respect to the prediction of radiation spectra emitted during the laser plasma interaction.
  • Invited lecture (Conferences)
    Laser and Plasma Accelerator Workshop 2013, 01.-06.09.2013, Goa, Indien
  • Invited lecture (Conferences)
    MAP Targetry Workshop, 09.-11.10.2013, München, Deutschland

Publ.-Id: 19249 - Permalink

The Prospect of Laser Accelerated Proton Pulses for Particle Tumor Therapy
Schramm, U.;
Demanding applications like radiation therpy of cancer have pushed the development of ultra-comnpact laser plasma proton accelerators and defined novel levels of control, beam transport in pulsed fields and monitoring capabilities in experiments. In this presentation the status of the joint activities of the Dresden groups at HZDR running the high power laser Draco and at Oncoray, the national center for radiation research in oncology, will be discussed. Emphasis will be given to the energy scaling of proton bunches accelerated in the TNSA regime with and during ultra-short pulses, potential instabilities in the process, methods for online monitoring, and to the status of the ongoing upgrade of Draco to PW power level.
  • Invited lecture (Conferences)
    ASET colloquium, 29.08.2013, Mumbai, Indien

Publ.-Id: 19248 - Permalink

Ion heating dynamics in solid buried layer targets irradiated by ultra-short intense laser pulses
Huang, L. G.; Bussmann, M.; Kluge, T.; Lei, A. L.; Yu, W.; Cowan, T. E.;
We investigate bulk ion heating in solid buried layer targets irradiated by ultra-short laser pulses of relativistic intensities using particle-in-cell simulations. Our study focuses on a CD2-Al-CD2 sandwich target geometry. We find enhanced deuteron ion heating in a layer compressed by the expanding aluminium layer. A pressure gradient created at the Al-CD2 interface pushes this layer of deuteron ions towards the outer regions of the target. During its passage through the target, deuteron ions are constantly injected into this layer. Our simulations suggest that the directed collective outward motion of the layer is converted into thermal motion inside the layer, leading to deuteron temperatures higher than those found in the rest of the target. This enhanced heating can already be observed at laser pulse durations as low as 100 fs. Thus, detailed experimental surveys at repetition rates of several ten laser shots per minute are in reach at current high-power laser systems, which would allow for probing and optimizing the heating dynamics.
Keywords: Ion heating dynamics, ultra-short intense lasers, particle in cell simualtions

Publ.-Id: 19247 - Permalink

Phenylacetylene Hydrogenation over [Rh(NBD)(PPh3)(2)]BF4 Catalyst in a Numbered-Up Microchannels Reactor
Al-Rawashdeh, M.; Zalucky, J.; Müller, C.; Nijhuis, T. A.; Hessel, V.; Schouten, J. C.;
This paper provides a proof of concept for the capability of the barrier-based micro-/millichannels reactor (BMMR) to number-up gas–liquid Taylor flow under reactive flow conditions. The hydrogenation of phenylacetylene to styrene and ethylbenzene using homogeneous cationic rhodium catalysts [Rh(NBD)(PPh3)2]BF4] (NBD = norbornadiene) was used as a model reaction. First, a parametric study in a semicontinuous batch reactor was made by changing the hydrogen pressure, the catalyst concentrations, and the initial concentrations of phenylacetylene and styrene. A mechanism for this reaction system has been proposed by Esteruelas et al. ( J. Org. Chem. 1998, 49−53). This mechanism was extended here to develop a kinetic model which predicts the experimental result within an accuracy of 20%. Catalyst deactivation was observed and incorporated in the kinetic model. Second, the reaction was conducted in the BMMR. The reactant and product concentrations of a single channel were compared to those of eight parallel channels combined. For 95% of the obtained results, the difference in concentrations between the single channel and the eight channels was within ±10% and depended on the gas and liquid flow rates. As a proof of concept, the number-up concept of gas–liquid Taylor flow in the BMMR under reactive flow conditions has been successfully realized.
Keywords: barrier-based micro-/millichannels reactor; Taylor flow; homogeneous hydrogenation
  • Industrial & Engineering Chemistry Research 52(2013)33, 11516-11526
    DOI: 10.1021/ie4009277

Publ.-Id: 19246 - Permalink

Studying the constancy of galactic cosmic rays using noble gas and radionuclides data on iron meteorites
Smith, T.; Leya, I.; Merchel, S.; Rugel, G.; Pavetich, S.;
The constancy of the galactic cosmic rays (GCR) is a long-standing question in meteorite research. Temporal variations in the GCR intensity might not only sheed light into the origin and evolution of the cosmic rays, it will also compromise systematic studies of the dynamics of small bodies in the solar system using exposure age histograms. Here we present the first results of our study to set-up a consistent exposure ages histogram for iron meteorites, which enables to search for periodic GCR variations. So far, the light noble gases He, Ne, Ar and the cosmogenic radionuclides 10Be, 26Al, and 36Cl have been measured, respectively by mass spectrometry in Bern and at the DREAMS facility [1], in 22 iron meteorites, mostly from group IIIAB. Though, some of the data are still preliminary and further data for 41Ca, 53Mn, and 60Fe are awaited, these data will provide some new information about the distribution of exposure ages among iron meteorites and therefore also on the temporal variability of the GCR.
[1] Akhmadaliev, S. et al. (2012) NIMB 294, 5–10.
Keywords: AMS, cosmic radiation, GCR, meteorite
  • Lecture (Conference)
    Joint meeting “Paneth Kolloquium” and workshop of the DFG special program “The first 10 million years of the solar system” (DFG SPP 1385), 21.-23.10.2013, Nördlingen, Deutschland

Publ.-Id: 19245 - Permalink

Magnetic control of Coulomb scattering and terahertz transitions among excitons
Bhattacharyya, J.; Zybell, S.; Eßer, F.; Helm, M.; Schneider, H.; Schneebeli, L.; Böttge, C. N.; Breddermann, B.; Kira, M.; Koch, S. W.;
Time-resolved terahertz quenching studies of the magnetoexcitonic photoluminescence from GaAs/AlGaAs quantum wells are performed. A microscopic theory is developed to analyze the experiments. Detailed experiment–theory comparisons reveal a remarkable magnetic-field controllability of the Coulomb and terahertz interactions in the excitonic system.
Keywords: exciton dynamics, terahertz, Magneto-excitons

Publ.-Id: 19244 - Permalink

Positron emission tomography in pebble beds. part 2: graphite particle deposition and resuspension
Barth, T.; Kulenkampff, J.; Bras, S.; Gründig, M.; Lippmann-Pipke, J.; Hampel, U.;
The release of radio-contaminated carbonaceous dust from the pebble bed of a high temperature reactor (HTR) plays a major role for the safety assessment of accidental scenarios. In the present investigation, graphite particle deposition and resuspension in a fluid dynamically scaled HTR pebble bed was studied by means of positron emission tomography (PET). The particle laden turbulent flow in a model pebble bed was generated by an air driven small-scale test facility at ambient conditions. The pebble bed geometry was recorded by a 3D gamma ray computed tomography (CT) scan. Technical graphite dust was radioactively labelled and dispersed into the turbulent flow field of the test facility. The flow scenarios were adapted to study particle deposition and resuspension in succession. Firstly, the radio-labelled graphite particles were dispersed at low fluid velocities to study the multilayer formation during a pure deposition regime. Afterwards, the aerosol generator was switched off and the fan speed was stepwise increased to induce particle resuspension. A time resolved 3D PET-CT overlay provides a complete insight into the particle multilayer formation and removal. Similarities to other particle deposition and resuspension studies in turbulent flows were found.

Publ.-Id: 19243 - Permalink

Baseline closure model for dispersed bubbly flow: bubble coalescence and breakup
Liao, Y.; Rzehak, R.; Lucas, D.; Krepper, E.;
Computational Fluid Dynamics (often abbreviated as CFD) has been becoming one indispensable tool in solving and analyzing of problems that involve fluid flows. Moreover, owing to ever-increasing computer power, the physical scale that can be resolved in a CFD simulation gets smaller and smaller. For example, in a simulation of gas-liquid flows using interface-tracking or interface-capturing methods gas-liquid interfaces can be resolved, where closure models neither for bubble-liquid nor for bubble-bubble are needed. However, the spread of such kind of approaches is retarded by the huge computational consumption. So far it can only be applied to quite small systems, where only a small number of bubbles and thus simple regular interfaces are included.
For problems at engineering or industrial scale, the Euler-Euler or two-fluid model (TFM) is still the most attractive one. However, new issues arise from the complete smearing of gas-liquid interfaces. In a TFM simulation results rely heavily on the applied closure relations, which reconstruct the information of bubble-liquid and bubble-bubble interactions. Furthermore, the effect of all the closures is coupled with each other. As a result, to assess the performance of one certain closure relation, e.g. coalescence and breakup of bubbles, under various flow conditions, a common set of other models should be defined. Otherwise, the wish of generally-applicable closures for TFM will always remain a dream.
On the other hand side, due to a variety of flow regimes and the complicated nature of physics, there exists not yet a consensus set of closure models, even for the simplest case of adiabatic bubbly flow. Rzehak et al. (2013) has taken the first step towards the goal by defining a so-called baseline model, which collects the best or most promising relations from the open literature for adiabatic bubbly flows. It includes bubble forces, bubble-induced turbulence (BIT), and bubble coalescence and breakup. The baseline model provides a common basis for further improvement and development of closure relations.
The focus of the present work is put on the new closures for bubble coalescence and breakup included in the baseline model, which was proposed originally in Liao et al. (2011). In order to guarantee the transferability all important mechanisms that lead to bubble coalescence and breakup are taken into account. In addition, the breakup model avoids successfully uncertainty introduced by separate daughter bubble size distribution functions. These have been believed to be major limitations in most existing models published in the open literature.
One major difficulty encountered in the validation of new bubble coalescence and breakup models is the superposition between coalescence and breakup as well as between multiple mechanisms in the reality. The strategy adopted in the current work is to select validation cases, where only coalescence is most important while the uncertainty brought by breakup is as few as possible. In addition, coalescence due to wake entrainment and eddy capture is negligible. Some test cases that satisfy the criterion approximately are found in the MTLoop experiments for air-water upward vertical pipe flows, which were carried out at the Helmholtz-Zentrum Dresden – Rossendorf a few years ago.
In the simulation, the new closures for bubble coalescence and breakup are implemented in the MUSIG approach (Krepper et al., 2008) provided by ANSYS CFX 14.0. With aid of measured evolution of bubble size distributions along the pipe, the performance of the new model within the baseline model is evaluated for several superficial gas and liquid velocities. The comparison between predictions and measurements demonstrates a promising agreement for all the investigated cases. In addition, considerable improvement against the default closure models available in ANSYS CFX is achieved. Nevertheless, huge validation work is still required to evaluate the breakup model as well as other coalescence mechanisms such as wake entrainment.
Keywords: Dispersed Bubbly Flow; Two-Fluid Model; Bubble Coalescence and Breakup; Kernel Functions; Baseline Closures
  • Lecture (Conference)
    International seminar on Subchannel Analysis, CFD modeling and verification and CHF experiment and benchmarking (ISACC), 03.-04.08.2013, Xian, China

Publ.-Id: 19242 - Permalink

New coalescence and breakup kernels for air-water and steam-water pipe flows
Liao, Y.; Lucas, D.; Krepper, E.; Rzehak, R.;
New coalescence and breakup rate kernel functions are tested in the frame of MUSIG approach for developing bubbly flows inside a vertical pipe. Two test cases are investigated in this work, one from the MTLoop air-water experiment and the other from TOPFLOW steam-water experiment. Both of them demonstrate that consideration of bubble coalescence and breakup can improve predictions considerably. Furthermore, the new models are able to deliver reliable results in both the air-water and steam-water cases without need to adjust the constants, while the widespread model combination predicts too large coalescence and breakup rates. However, there is still a long way to go before a generally-applicable set of constants in the new models is achieved.
Keywords: New Bubble Coalescence and Breakup Kernels; Air-Water; Steam-Water; Vertical Pipe Flows
  • Lecture (Conference)
    5th Population Balance Modeling Conference (PBM2013), 11.-13.09.2013, Bangalore, India
  • Contribution to proceedings
    5th Population Balance Modeling Conference (PBM2013), 11.-13.09.2013, Bangalore, India

Publ.-Id: 19241 - Permalink

Effects of inlet condition on flow structure of bubbly flow in rectangular column
Akbar, M. H. B. M.; Hayashi, K.; Tomiyama, A.; Lucas, D.;
Experiments on bubbly flows in a rectangular column are carried out to investigate effects of inlet condition on flow structure. An air diffuser having 35 nozzles is used. The inlet gas flow rates from 34 nozzles are uniform and the lift coefficients of bubbles are small at this flow rate, whereas the gas inflow from the remaining one nozzle is varied to change the sign and magnitude of lift coefficients. The main conclusions obtained are as follows: (1) bubbly flow in a bubble column is apt to be heterogeneous even with small non-uniformity in the distribution of gas inflow, (2) when the nozzle causing non-uniform gas inflow is located in the center of the diffuser plate and the inflow distribution is symmetric, heterogeneous structure is formed due to the lift-induced flow instability pointed out by Lucas et al., (3) when the nozzle causing non-uniform gas inflow is located near the side wall of the column and the inflow distribution is asymmetric, heterogeneous structure is induced by the Coanda effect, and (4) a multi-fluid model can predict the effects of non-uniform gas inflow on the formation of heterogeneous structure in bubbly flow.
Keywords: Bubbly flow, Flow instability, Bubble, Bubble column, Multi-fluid model
  • Contribution to proceedings
    8th World Conference on Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics, 16.-20.06.2013, Lisbon, Portugal

Publ.-Id: 19240 - Permalink

Characterization of self-damaged (U,Pu)N fuel used in the NIMPHE program
Carvajal-Nunez, U.; Prieur, D.; Janssen, A.; Wiss, T.; Cambriani, A.; Vermorel, E.; Scheinost, A.; Somers, J.;
During in-pile, irradiation-induced damage occurs in nuclear fuel and results in a deterioration of its properties, which can affect the margin to melt of the fuel. Damage also occurs in fresh fuel through the self-irradiation process, and thus provides a convenient means to investigate changes in the material. A uranium–plutonium mixed nitride fuel made over 25 years ago, and stored in the ITU archives has been retrieved. Coupling EXAFS and TEM has shown that this material was still well-crystallized. However, an increase of 0.3% of the lattice parameter was found. As shown by the EXAFS, the U–N and Pu–N as well as the metal–metal distances are similarly affected. However, no significant modification of both anion and cation sublattice was found. Although no defect clustering was found by EXAFS, the presence of nanometric helium bubbles was demonstrated by TEM as well as nanometric disordered domains.
Keywords: nuclear fuel EXAFS

Publ.-Id: 19239 - Permalink

Biosorption of heavy metals and nanoparticles by Gram-positive bacteria and cellular components
Suhr, M.; Matys, S.; Viacava Romo, K. E.; Raff, J.; Pollmann, K.;
Bacterial isolates from the uranium mining waste pile Haberland (Johanngeorgenstadt, Saxony) possess high affinities to heavy metals e.g. uranium. This binding effect is caused by the components of the bacterial cell wall, mainly affected by surface layer proteins.
In this work we studied the metal uptake of different environmental relevant heavy and noble metals and metaloids as well as nanoparticles by living bacterial cells of a Gram-positive strain and its isolated primary cellular components (e.g. membrane lipids, peptidoglycan, s-layer proteins). This was done via batch experiments and the results were obtained by ICP-MS measurements.
The quartz crystal microbalance with dissipation monitoring was introduced to track the adsorption of biological molecules and to study the metal and nanoparticle interaction with the single cell wall components. With this method it was able to detect the sorption processes on a molecular level in real time and to obtain further information to metal interaction processes and to viscoelastic properties. Partially supporting atomic force microscopy (AFM) studies enable the imaging of bio nanostructures and reveal complex information of structural properties.
Keywords: Biosorption, bacteria, QCM-D, ICP-MS, s-layer, proteins, lipids, heavy metals, nanoparticles
  • Poster
    8th HZDR PhD Seminar, 07.-09.10.2013, Bautzen, Germany

Publ.-Id: 19237 - Permalink

Preliminary investigations on the determination of three-dimensional dose distributions using scintillator blocks and optical tomography
Kroll, F.; Pawelke, J.; Karsch, L.;
Purpose: Clinical QA in teletherapy as well as the characterization of experimental radiation sources for future medical applications requires effective methods for measuring three-dimensional (3D) dose distributions generated in a water-equivalent medium. Current dosimeters based on ionization chambers, diodes, thermoluminescence detectors, radiochromic films, or polymer gels exhibit various drawbacks: High quality 3D dose determination is either very sophisticated and expensive or requires high amounts of effort and time for the preparation or read out. New detectors based on scintillator blocks in combination with optical tomography are studied, since they have the potential to facilitate the desired cost-effective, transportable, and long-term stable dosimetry system that is able to determine 3D dose distributions with high spatial resolution in a short time.

Methods: A portable detector prototype was set up based on a plastic scintillator block and four digital cameras. During irradiation the scintillator emits light, which is detected by the fixed cameras. The light distribution is then reconstructed by optical tomography, using maximum-likelihood expectation maximization. The result of the reconstruction approximates the 3D dose distribution. First performance tests of the prototype using laser light were carried out. Irradiation experiments were performed with ionizing radiation, i.e., bremsstrahlung (6 to 21 MV), electrons (6 to 21 MeV), and protons (68 MeV), provided by clinical and research accelerators.

Results: Laser experiments show that the current imaging properties differ from the design specifications: The imaging scale of the optical systems is position dependent, ranging from 0.185 mm/pixel to 0.225 mm/pixel. Nevertheless, the developed dosimetry method is proven to be functional for electron and proton beams. Induced radiation doses of 50 mGy or more made 3D dose reconstructions possible. Taking the imaging properties into account, determined dose profiles are in agreement with reference measurements. An inherent drawback of the scintillator is the nonlinear light output for high stopping-power radiation due to the quenching effect. It impacts the depth dose curves measured with the dosimeter. For single Bragg peak distributions this leads to a peak to plateau ratio of 2.8 instead of 4.5 for the reference ionization chamber measurement. Furthermore, the transmission of the clinical bremsstrahlung beams through the scintillator leads to the saturation of one camera, making dose reconstructions in that case presently not feasible.

Conclusions: It is shown that distributions of scintillation light generated by proton or electron beams can be reconstructed by the dosimetry system within minutes. The quenching apparent for proton irradiation, and the yet not precisely determined position dependency of the imaging scale, require further investigation and corrections. Upgrading the prototype with larger or inorganic scintillators would increase the detectable proton and electron energy range. The presented results show that the determination of 3D dose distributions using scintillator blocks and optical tomography is a promising dosimetry method.
Keywords: biomedical equipment, biomedical optical imaging, bremsstrahlung, cameras, dosimeters, dosimetry, expectation-maximisation algorithm, image reconstruction, ionisation chambers, laser applications in medicine, medical image processing, optical tomography, portable instruments, radiation quenching, radiation therapy, solid scintillation detectors, 3D dosimetry, scintillator, optical tomography, teletherapy

Publ.-Id: 19236 - Permalink

Untersuchung von Szintillationsdetektoren für Prompt Gamma Imaging Systeme zur Verifikation der Dosisdeposition in der Protonentherapie
Römer, K.; Petzoldt, J.; Pausch, G.; Rohling, H.; Hertel, N.; Fiedler, F.;
Fragestellungen: Bei der Therapie von Tumorpatienten mit Partikelstrahlen ist ein exaktes und promptes Verfahren zur Überwachung der applizierten Dosisverteilung unerlässlich. Ein vielversprechender Ansatz ist die Messung Gammastrahlung, die – im Gegensatz zur Annihilationsstrahlung beim In-Beam-PET – ohne Zeitverzögerung abgestrahlt wird. Das entsprechende Gammaenergiespektrum ist jedoch sehr komplex, hochenergetischer als gängige im Labor zur Verfügung stehende Gammaquellen, und wird mit einer hohen Rate emittiert. Eine mögliche Lösung dieses Problems liefert die Compton Kamera. Jedoch sind diese Systeme sehr komplex und noch weit vom klinischen Einsatz entfernt. Sie erfordern Detektoren mit sehr guter Energieauflösung und spektroskopischer Elektronik. Eine Alternative bietet das Coded Aperture Prinzip. Hier wird eine möglichst stark absorbierende Maske vor dem ortsauflösenden Detektor angebracht, und es erfolgt eine ortsaufgelöste Zählung der Gammaquanten hinter der Maske. Auf eine genaue Energiemessung kann verzichtet werden, so dass die Anforderungen an Detektoren und Elektronik deutlich geringer ist. Kernstück aller Prompt Gamma Imaging Systeme unabhängig vom Messprinzip sind geeignete Detektoren für hochenergetische Gammastrahlung in Kombination mit einer geeigneten Elektronik. Diese Systemkomponenten müssen für den Einsatz unter den Bedingungen einer Partikeltherapie optimiert und charakterisiert werden, wobei Faktoren wie Energiebereich, Energieauflösung, Zählratenfestigkeit und Zeitauflösung entscheidend sind.

Material und Methoden: Standardisierte Proben verschiedener Szintillatormaterialien werden zunächst mit einem Referenz-Photomultiplier gekoppelt und mit klassischer Laborelektronik mit Hilfe radioaktiver Quellen bezüglich Photoelektronen-Ausbeute und Energieauflösung charakterisiert. Die Untersuchung weiterer Proben aus den gleichen Materialien in Abmessungen und Geometrien, die für ortsauflösende Messungen mit Silizuim-Photodetektoren eignen, mit derselben Technik erlaubt es dann, den Einfluß der Detektorgeometrie auf diese Parameter zu ermitteln. Schließlich lässt sich der Einfluss des Photosensors auf Energie-, Orts- und Zeitauflösung quantifizieren, wenn die vorher charakterisierten Proben mit unterschiedlichen, modernen Silizium-Photodetektoren ausgemessen werden. Die gewonnenen Erkenntnisse sollen es gestatten, für den jeweiligen Einsatzfall eine optimale Szintillator-Photosensor-Kombination zu wählen.

Ergebnisse: Erste Szintillatormaterialien wurden mit Hilfe des Referenz-Photomultipiers (XP5500/B von Photonis) hinsichtlich ihrer Photoelektronen-Produktion charakterisiert. NaI(Tl) hat demnach eine Ausbeute von >9000 Photoelektronen pro MeV. GAGG, das eigentlich mehr Licht liefern sollte, dessen Wellenlänge mit 510nm aber für die Effizienz der Photokathode ungünstiger ist, liefert >6000 Photoelektronen pro MeV. Diese nunmehr bekannten Szintillatoren werden dann mit Hilfe des digitalen Silizium-Photomultipliers (dSiPMT) der Firma Philips Digital Photon Counting auf ihre Einsatzmöglichkeit in ortsauflösenden Systemen getestet. Erste Messungen wurden auch mit analogen Silizium-Photomultipliern (SiPMT) oder Avalanche-Photodioden (APD) durchgeführt. Vergleiche mit Geant4 Simulationen zur Nachweiseffizienz und Lichtsammlung werden kurz vorgestellt.

Zusammenfassung: Die bildgebende Messung prompter Gammastrahlung ist ein vielversprechendes Verfahren zur Verifikation von Tumortherapien mit Partikelstrahlung. Entsprechende Messsysteme werden zurzeit entwickelt, benötigen aber maßgeschneiderte Detektoren. Diese Arbeit präsentiert Verfahren und erste Ergebnisse zur Charakterisierung von Szintillationsdetektoren für solche Systeme. Die systematische Untersuchung verschiedener Kristalle mit unterschiedlichen Photosensoren erlaubt dabei die Entkopplung von Material-, Geometrie- und Lichtdetektor-Effekten und damit eine Optimierung der Eigenschaften von Szintillationsdetektoren für die jeweilige Anwendung.

[1] G. F. Knoll, “Radiation Measurements”, Eds. John Wiley & Sons, New York, Third Edition, pp. 629-631, 2000.
[2] Z. Guzik, S. Borsuk, K. Traczyk, and M. Plominski, “TUKAN-an 8k pulse-height analyzer and multichannel scaler with a PCI or a USB interface”, IEEE Trans. Nucl. Sci., vol 53, pp. 231-235, 2006.
[3] M. Bertollaccini, S. Cova, and C. Bussolatti, “A technique for absolute measurement of the effective photoelectron per keV yield in scintillation counters”, Proceedings of the Nuclear Electronics Symposium, Versailles, France, 1968.
[4] S. Agostinelli et al., “GEANT4: A simulation toolkit. ”, Nucl. Instrum. Meth., A506:250–303, 2003.
[5] Saint Gobain, Brillance 380 Data Sheet.
[6] C. Plettner et al, “CaF 2 (Eu): An “Old” Scintillator Revisited”, Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE
[7] T. Frach et al, “The digital silicon photomultiplier — Principle of operation and intrinsic detector performance”, Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE, pp.1959,1965, Oct. 24 2009-Nov. 1 2009
[8] T. Kormoll et al, “In-Vivo Dosimetry for Photon Radiotherapy Based on Pair Production”, Nuclear Science, IEEE Transactions on , vol.57, no.3, pp.1125,1131, June 2010
Keywords: proton therapy, in-vivo dosimetry, scintillator
  • Lecture (Conference)
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP 2013), 18.-21.09.2013, Köln, Deutschland
  • Open Access LogoAbstract in refereed journal
    Medizinische Physik 2013 (2013), 322-323

Publ.-Id: 19235 - Permalink

Detectors for monitoring
Fiedler, F.;
no abstract available
Keywords: detectors, in-vivo dose monitoring, proton therapy, ion therapy
  • Invited lecture (Conferences)
    ENTERVISION Course: Detectors and electronics, 09.-13.09.2013, Valencia, Spanien

Publ.-Id: 19234 - Permalink

Neue bildgebende Systeme für die Partikeltherapie - Ergebnisse des EU-Projektes ENVISION
Fiedler, F.;
Einleitung: Die Partikeltherapie ist eine neue und hoch entwickelte Technik der Strahlentherapie bei Krebs. Strahlen geladener Teilchen, also Protonen und Ionen, werden verwendet, um Tumorzellen zu zerstören. Diese Ionenstrahlen deponieren ihre Energie primär am Ende ihres Weges im sogenannten Bragg-Peak. Dadurch gelingt es, eine hohe Koformalität zu erreichen und gesundes Gewebe sowie insbesondere strahlenempfindliche Organe optimal zu schonen. Um jedoch die Vorteile dieser Therapieform vollständig nutzen zu können, ist ein Verfahren erforderlich, welches den Ort der Dosisdeposition verifiziert. Hierfür wurde die Methode der Positronen-Emissions-Tomographie (PET) angewendet, die bei der Bestrahlung entstehende Sekundärteilchen detektiert und damit eine qualitative Bewertung der Dosisapplikation ermöglicht. An mehreren Zentren weltweit wird dieses Verfahren derzeit klinisch angewendet [1-3]. Eine andere, in der Entwicklung befindliche Möglichkeit ist die Einzelphotonentomographie (in-beam SPECT) [4-7], für welch neuartige Detektorkonfigurationen erforderlich sind.
Materialien und Methoden: Um die Instrumente für die Qualitätssicherung in der Partikeltherapie zu verbessern, stellt die Europäische Kommission die Finanzierung für ein 4-Jahres-Projekt, ENVISION - European NoVel Imaging Systems for ION therapy (Grant Agreement Number 241 851), bereit. Das Ziel des Projektes ist die Entwicklung von
(i) Echtzeit-Überwachung der Dosisapplikation;
(ii) quantitativer Bildgebung und präziser Bestimmung der abgegebenen Dosis;
(iii) schnellem Feedback für die optimale Planung der Behandlung;
(iv) der Anwendung des Verfahren auf bewegte Zielvolumina;
(v) Simulationsstudien.
Das Projekt startete Februar 2010 und ist ein Zusammenschluss von 16 führenden europäischen Forschungszentren und Industriepartnern mit einem Budget von 6 Millionen Euro, die Koordination obliegt dem CERN.
Ergebnisse: In Rahmen dieses Projektes wurden Simulationsstudien zur optimalen Auslegung eines für das Dosismonitoring geeigneten Detektors durchgeführt. Sowohl für PET als auch für SPECT wurden mehrere konzeptionell verschiedene Prototypen an den Partnerinstituten aufgebaut und an Bestrahlungsanlagen getestet. Die PET Methode wurde für bewegte Zielvolumina adaptiert und in Phantomexperimenten erfolgreich angewendet. Um die klinische Nutzbarkeit zu verbessern, wurde ein Softwareprototyp zur semiautomatischen Auswertung entwickelt.
Zusammenfassung: ENVISION ermöglichte die Realisierung verschiedener Ansätze und Ideen, existierende Verfahren für das Dosismonitoring zu verbessern und neue Methoden in Prototypen zu überführen. Insbesondere für die neuartigen Verfahren sind weitere Tests und Entwicklungen nötig, um das klinische Potential vollständig abschätzen zu können. Ferner ist die Integration der neuen Verfahren in den klinischen Alltag ein wichtiges Ziel künftiger Arbeiten.
[1] W. Enghardt et al.: Nucl. Instr. Meth. A 525 (2004) 284.
[2] T. Nishio et al.: Med. Phys. 33 (2006) 4190.
[3] K. Parodi et al.: Int. J. Radiat. Oncol. Biol. Phys. 68 (2007) 920.
[4] C.H. Min et al.: Appl. Phys. Lett. 89 (2006), 183517.
[5] T. Kormoll et al.: Nucl. Instr. Meth. A 626-627 (2011) 114.
[6] J.C. Polf et al.: Phys. Med. Biol. 54 (2009) N519-27.
[7] J. Smeets et al.: Phys. Med. Biol. 57 (2012) 3371.
Keywords: Partikeltherapie, in-vivo dose monitoring, ENVISION
  • Invited lecture (Conferences)
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP 2013), 18.-21.09.2013, Köln, Deutschland
  • Open Access LogoAbstract in refereed journal
    Medizinische Physik 2013 (2013), 275

Publ.-Id: 19233 - Permalink

Tomographic Positron Annihilation Lifetime Spectroscopy
Wagner, A.; Anwand, W.; Butterling, M.; Fiedler, F.; Fritz, F.; Kempe, M.; Cowan, T. E.;
Positron annihilation lifetime spectroscopy serves as a perfect tool for studies of open-volume defects in solid materials such as vacancies, vacancy agglomerates, and dislocations. Moreover, structures in porous media can be investigated ranging from 0.3 nm to 30 nm employing the variation of the Positronium lifetime with the pore size. While lifetime measurements close to the material’s surface can be performed at positron-beam installations bulk materials, fluids, bio-materials or composite structures cannot or only destructively accessed by positron beams. Targeting those problems, a new method of non-destructive positron annihilation lifetime spectroscopy has been developed which features even a 3-dimensional tomographic reconstruction of the spatial lifetime distribution.
A beam of intense bremsstrahlung is provided by the superconducting electron linear accelerator ELBE (Electron Linear Accelerator with high Brilliance and low Emittance) at Helmholtz-Zentrum Dresden-Rossendorf which delivers continuous wave electron bunches of less than 10 ps temporal width and an adjustable bunch separation of multiples of 38 ns, average beam currents of up to 1.6 mA, and energies up to 16 MeV. Since the generation of bremsstrahlung and the transport to the sample preserves the sharp timing of the electron beam, positrons generated inside the entire sample volume by pair production feature a sharp start time stamp for lifetime studies. In addition to the existing technique of in-situ production of positrons inside large (cm3) bulk samples using high-energy photons up to 16 MeV from bremsstrahlung production [1], granular position-sensitive photon detectors [2] have been employed.
In the presentation, the detector system [3] will be described and results for experiments using samples with increasing complexity will be presented. The Lu2SiO5:Ce scintillation crystals allow resolving the total energy to 5.1 % (RMS) and the annihilation lifetime to 225 ps (RMS). 3-dimensional annihilation lifetime maps have been created in an offline-analysis employing well-known techniques from PET. Further work concentrates on transferring the analysis to a massively parallel GPU-array.

[1] M. Butterling et al., Nucl. Instr. Meth. Phys. Res. B 269(2011) 2623.
[2], Siemens Medical, ACCEL II HiRez block detector.
[3] A. Wagner et al., Defect and Diffusion Forum 331 (2012) 41.
Keywords: Positron annihilation lifetime spectroscopy, non-destructive 3-dimensional tomographic reconstruction, spatial lifetime distribution, bremsstrahlung, superconducting electron, linear accelerator ELBE
  • Invited lecture (Conferences)
    13th International Workshop on Slow Positron Beam Techniques and Applications, 15.-20.09.2013, München, Deutschland
  • Open Access LogoJournal of Physics: Conference Series 505(2014), 012034
    DOI: 10.1088/1742-6596/505/1/012034

Publ.-Id: 19232 - Permalink

Native Cu from the oceanic crust: Isotopic insights into native metal origin
Dekov, V. M.; Rouxel, O.; Asael, D.; Hålenius, U.; Munnik, F.;
Ocean drilling has revealed that, although a minor mineral phase, native Cu ubiquitously occurs in the oceanic crust. Cu isotope systematics for native Cu from a set of occurrences from volcanic basement and sediment cover of the oceanic crust drilled at several sites in the Pacific, Atlantic and Indian oceans constrains the sources of Cu and processes that produced Cu0. We propose that both hydrothermally-released Cu and seawater were the sources of Cu at these sites. Phase stability diagrams suggest that Cu0 precipitation is favored only under strictly anoxic, but not sulfidic conditions at circum-neutral pH even at low temperature. In the basaltic basement, dissolution of primary igneous and potentially hydrothermal Cu-sulfides leads to Cu0 precipitation along veins. The restricted Cu-isotope variations (δ65Cu = 0.02 – 0.19‰) similar to host volcanic rocks suggest that Cu0 precipitation occurred under conditions where Cu+-species were dominant, precluding Cu redox fractionation. In contrast, the Cu-isotope variations observed in the Cu0 from sedimentary layers yield larger Cu-isotope fractionation (δ65Cu = 0.41 – 0.95‰) suggesting that Cu0 precipitation involved redox processes during the diagenesis, with potentially seawater as the primary Cu source. We interpret that native Cu precipitation in the basaltic basement is a result of low temperature (20°-65°C) hydrothermal processes under anoxic, but not H2S-rich conditions. Consistent with positive δ65Cu signatures, the sediment cover receives major Cu contribution from hydrogenous (i.e., seawater) sources, although hydrothermal contribution from plume fallout cannot be entirely discarded. In this case, disseminated hydrogenous and/or hydrothermal Cu might be diagenetically remobilized and reprecipitated as Cu0 in reducing microenvironment.
Keywords: Cu-isotopes; Deep-Sea Drilling Project; native Cu; Ocean Drilling Project; oceanic crust alteration

Publ.-Id: 19231 - Permalink

Liquid-Solid Mass Transfer in a Tubular Reactor with Solid Foam Packings
Mohammed, I.; Bauer, T.; Schubert, M.; Lange, R.;
Catalytically active open-cell solid foam packings are promising replacements for conventional randomly packed catalyst particles due to their low pressure drop and high specific surface area. The liquid-solid mass transfer was studied with a modified electrochemical diffusion current method for different packings and flow rates. The effective liquid-solid mass transfer coefficients (Ф • kLS ) were determined at two different axial packing positions. In particular, the effects of gas and liquid superficial velocities and the pre-wetting mode of the packing (‘LEVEC’ and ‘KAN-LIQUID’) were researched. The results reveal that higher liquid superficial velocity increases the liquid-solid mass transfer, while increasing foam pore density lowers the mass transfer rate. The strong multiplicity behavior known from hydrodynamic studies of Mohammed et al. (2013) was not obtained for the liquid-solid mass transfer. However, the type of the liquid distributor providing the initial irrigation pattern has a significant effect on the effective liquid-solid mass transfer coefficient. A new correlation is proposed to predict the effective liquid-solid mass transfer coefficient.
Keywords: solid foam, liquid-solid mass transfer, electrochemical method, pre-wetting mode, packed-bed reactor, multiphase reactor

Publ.-Id: 19230 - Permalink

Characterization of narrow bandwidth x-rays from a Laser-Thomson-Backscattering source
Jochmann, A.;
A tunable source of intense ultra-short hard X-ray pulses represents a novel tool for the structural analysis of complex systems with unprecedented temporal and spatial resolution. With the simultaneous availability of a high power short-pulse laser system this provides unique opportunities at the forefront of relativistic light–matter interactions. At Helmholtz-Zentrum Dresden-Rossendorf (HZDR) we demonstrated the principle of such a light source (PHOENIX – Photon Electron collider for Narrow bandwidth Intense X-Rays) 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 reliably adjusted from 12 keV to 20 keV by tuning the electron energy (24–30 MeV). Ensuring the spatial–temporal overlap at the interaction point and suppressing the Bremsstrahlung background a signal to noise ratio of greater than 300 was reached.
Keywords: Laser backscattering; X-ray; Linear accelerator; Inverse Compton; Ultrafast; Thomson scattering
  • Lecture (Conference)
    The 5th International Conference "Channeling 2012", "Charged & Neutral Particles Channeling Phenomena", 23.-28.09.2012, Alghero, Italia

Publ.-Id: 19229 - Permalink

Operation of a picosecond narrow-bandwidth Laser-Thomson-backscattering X-ray source
Jochmann, A.; Irman, A.; Lehnert, U.; Couperus, J. P.; Kuntzsch, M.; Trotsenko, S.; Wagner, A.; Debus, A.; Schlenvoigt, H.; Helbig, U.; Bock, S.; Ledingham, K.; Cowan, T.; Sauerbrey, R.; Schramm, U.;
A tunable source of intense ultra-short hard X-ray pulses represents a novel tool for the structural analysis of complex systems with unprecedented temporal and spatial resolution. With the simultaneous availability of a high power short-pulse laser system this provides unique opportunities at the forefront of relativistic light–matter interactions. At Helmholtz-Zentrum Dresden-Rossendorf (HZDR) we demonstrated the principle of such a light source (PHOENIX – Photon Electron collider for Narrow bandwidth Intense X-Rays) 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 reliably adjusted from 12 keV to 20 keV by tuning the electron energy (24–30 MeV). Ensuring the spatial–temporal overlap at the interaction point and suppressing the Bremsstrahlung background a signal to noise ratio of greater than 300 was reached.
Keywords: Laser backscattering; X-ray; Linear accelerator; Inverse Compton; Ultrafast; Thomson scattering

Publ.-Id: 19228 - Permalink

Spectral investigations of Laser-wakefield accelerator dynamics and advanced brilliant light sources
Debus, A.; Steiniger, K.; Zarini, O.; Pausch, R.; Widera, R.; Bussmann, M.; Cowan, T.; Schramm, U.; Sauerbrey, R.;
In order to improve quality and reproducibility of electron beams by Laser-wakefields acceleration (LWFA) for brilliant X-ray sources, at the HZDR we investigate the radiation emitted by LWFA and the resulting electron beams both in theory and experiment.

Experimentally, we are currently setting up an ultra-broadband, staggered spectrometer system ranging from the UV (200 nm) to the mid-IR (12µm) for analyzing coherent transition radiation from electron bunches to infer bunch durations and temporal structures down to sub-fs resolution at single-shot.

Aiming for a quantitative understanding of spectral signatures emitted by LWFA in arbitrary directions, we have added a Liénard-Wiechert type radiation module to the PIConGPU code for calculating online, spectral "sky-maps", as well as logarithmic spectra from IR to X-ray energies, using all particles of a 3D-PIC simulation.

Towards an optical FEL, either by conventional or LWFA electrons, we discuss design goals and feasibility of Travelling-wave Thomson scattering geometries.
Keywords: Laser-wakefield accelerator, LWFA, brilliant x-ray sources, optical FEL, TWTS, Traveling-wave Thomson scattering, electron bunch duration, coherent transition radiation, CTR, single-shot spectrometer
  • Poster
    Physics and Applications of High Brightness Beams (HBEB) 2013, 25.-28.3.2013, San Juan, Puerto Rico

Publ.-Id: 19227 - Permalink

A Spectral Sky Map of Laser Wakefield Acceleration
Debus, A.; Pausch, R.; Widera, R.; Bussmann, M.; Schramm, U.;
We present an add-on to our GPU-based 3D particle-in-cell (PIC) code PIConGPU. This add-on allows to compute the radiation far field of all particles in the simulation using Liénard-Wiechert potentials.
With this code it is possible to compute a complete spectral sky map of all the radiation emitted during laser-driven wakefield acceleration of electrons in a plasma. We have implemented the calculation in such a way that it allows us to compute spectra with logarithmic frequency scales from the infrared to the X-ray region. Furthermore, we discuss the techniques involved to implement the algorithm on GPUs and present scaling results on large GPU clusters.
Keywords: particle-in-cell code, PIC, GPU, laser-wakefield accelerators, plasma radiation, Liénard-Wiechert potentials
  • Poster
    GPU Technology Conference 2013, 18.-21.3.2013, San Jose, California, United States of America

Publ.-Id: 19226 - Permalink

Simulating radiation from Electron beams to full Laser-plasmas
Debus, A.; Pausch, R.; Steiniger, K.; Hübl, A.; Burau, H.; Widera, R.; Bussmann, M.; Cowan, T.; Jochmann, A.; Couperus, J. P.; Irman, A.; Schramm, U.;
We show the results and its numerical analysis using CLARA from the recent Thomson scattering experiment with DRACO and ELBE. Extending the scope to the prediction and analysis of plasma radiation from Laser plasmas, we present PIConGPU with its capability of calculating the radiation from all billions of macro particles in the simulation. This is illustrated with simulation results of Laser-wakefield acceleration and the Kelvin-Helmholtz instability, which was shown to scale up to petaflop performance on the TITAN cluster at Oakridge.
Keywords: Thomson scattering, Liénard-Wiechert potentials, petaflop, HPC, X-ray, Laser-wakefield accelerator, Kelvin-Helmholtz instability, particle-in-cell code
  • Lecture (Conference)
    Laboratory for Laser- and beam-driven plasma Acceleration (LAOLA) Workshop, 28.-29.5.2013, Wismar, Deutschland

Publ.-Id: 19225 - Permalink

Petaflop Plasma Simulations
Debus, A.; Pausch, R.; Widera, R.; Hübl, A.; Burau, H.; Kluge, T.; Schmitt, F.; Juckeland, G.; Nagel, W.; Bernholdt, D. E.; Schuchart, J.; Bussmann, M.; Cowan, T.; Sauerbrey, R.;
Current results and performance scalings (strong and weak) are presented from simulating the Kelvin-Helmholtz instability including emitted radiation using PIConGPU on the Oakridge TITAN cluster.
Keywords: plasma radiation, Kelvin-Helmholtz instability, petaflop, HPC, Particle-in-cell code
  • Poster
    Helmholtz International Beamline for Extreme Fields (HIBEF), 02.-5.6.2013, Hamburg, Deutschland
  • Lecture (Conference)
    Helmholtz International Beamline for Extreme Fields (HIBEF), 02.-5.6.2013, Hamburg, Deutschland

Publ.-Id: 19224 - Permalink

Synthesis of coffinite, USiO4, and structural investigations of the UxTh(1-x)SiO4 solid solutions
Labs, S.; Hennig, C.; Weiss, S.; Curtius, H.; Zaenker, H.; Bosbach, D.;
The miscibility behavior of the USiO4 – ThSiO4 system was investigated. The end members and ten solid solutions UxTh(1-x)SiO4 with x = 0.12 – 0.92 were successfully synthesized, without formation of other secondary uranium or thorium phases. Lattice parameters of the solid solutions evidently follow Vegard's Law. Investigation of the local structure with EXAFS reveals small differences between U and Th environment attributed to different atomic radii of the metal atoms but no implications for a miscibility gap. The data provided confirms complete miscibility for the system USiO4 – ThSiO4. The structure of the end members was studied in detail with XRD and discussed with special regard to the oxygen positions and the often neglected Si-O bond length. USiO4 could be obtained without UO2 impurities and the lattice parameters derived from Rietveld refinement as c = 6.2606(3) Å and a = 6.9841(3) Å. The Si-O distance in USiO4 appears to be 1.64 Å, which is more reasonable than earlier reported values.
Keywords: coffinite, thorite, solid solution, structural properties

Publ.-Id: 19223 - Permalink

Radiative Particle-in-Cell Simulations: Shedding new Light into the Dynamics of Laser-plasma interactions
Debus, A.; Pausch, R.; Steiniger, K.; Hübl, A.; Burau, H.; Widera, R.; Kluge, T.; Schramm, U.; Cowan, T. E.; Bussmann, M.; Schneider, B.; Grottel, S.; Schmitt, F.; Hönig, W.; Juckeland, G.; Nagel, W.;
We present recent results using PIConGPU, a fully relativistic 3D particle-in-cell (PIC) code running on GPU clusters. We extended our code to compute the radiation spectra of all particles in the simulation based on classical Liénard-Wiechert potentials including full coherence and polarisation properties. We discuss implementation, physics tests, scaling and show simulation results of laser-wakefield accelerator and astrophysical plasmas, for which we calculated the angularly resolved spectra ranging from infrared to X-ray wavelengths.

Such an extensive treatment of plasma radiation across billions of macro particles makes it possible to explore temporally resolved plasma radiation spectra on linear and logarithmic photon energy scales over large solid angles ("sky-maps").
This ability of obtaining quantitative spectral data in plasma simulations poses a unique tool for determining the phase space distribution of electrons. Since spectral information is readily accessible in experiments, our results can serve as a valuable input to new diagnostics.

For the petaflop perfomance scaling of PIConGPU on the Oak Ridge TITAN cluster we use a scenario of the Kelvin-Helmholtz instability including radiation. Furthermore, we demonstrate the usefulness of the live 3D visualisation feature of PIConGPU for accessing running simulations.
Keywords: HPC, plasma radiation, particle-in-cell simulation, petaflop, 3D live visualization, Kelvin-Helmholtz instability, Laser-wakefield accelerator
  • Invited lecture (Conferences)
    23rd International Conference on Numerical Simulation of Plasmas (23rd ICNSP), 14.-16.9.2013, Beijing, China

Publ.-Id: 19222 - Permalink

Interactions of Plutonium with a Typical Isolate from Mont Terri Opalinus Clay
Moll, H.; Lütke, L.; Bachvarova, V.; Cherkouk, A.; Selenska-Pobell, S.; Bernhard, G.;
Clay is investigated as one potential host rock for a safe disposal of nuclear waste. In this talk, results will be presented and discussed describing the bacterial diversity in Mont Terri Opalinus clay, the enrichment and cultivation of bacterial clay isolates and the interactions of a specific novel Sporomusa sp. isolate with plutonium.
Keywords: diversity, bacteria, plutonium
  • Lecture (others)
    5. Workshop des Verbundprojekts „Rückhaltung endlagerrelevanter Radionuklide im natürlichen Tongestein und in salinaren Systemen“, 30.09.-01.10.2013, Potsdam, Deutschland

Publ.-Id: 19221 - Permalink

Shear induced force on a bubble in a bubble swarm
Ziegenhein, T.;
The lift force on a single bubble changes it sign with increasing Eo-Number
Lift formulation, Tomiyama:
𝐹_𝐿𝑖𝑓𝑡= −𝐶_𝐿 𝜌_𝐿 𝛼_𝐺 (𝒗_(𝐵𝑢𝑏.)−𝒗_𝐿𝑖𝑞 ) dv_Liq/𝑑𝑥
𝐶_𝐿≅0.6−0.1𝐸𝑜_𝐻 , 4≤𝐸𝑜_𝐻≤8
Hypothesis: The sign change occur through vortex shedding at the bubble in a shear field
Keywords: bubbly flow, closure models, lift force, bubble column
  • Poster
    HZDR PHD-Seminar, 07.-09.10.2013, Bautzen, Deutschland

Publ.-Id: 19220 - Permalink

Liquid Metal Experiments for the Visualisation of the Two-phase flow in a Continuous Casting Model
Timmel, K.; Shevchenko, N.; Röder, M.; Eckert, S.; Gerbeth, G.; Anderhuber, M.; Gardin, P.;
The quality of continuous casted steel is significantly affected by the flow pattern in the mould and the SEN. The flow in continuous casting machines is often a two-phase one, because argon bubbles are injected into the melt to avoid clogging inside the casting nozzle. Dependent on process parameters, like the liquid and the gas flow rate, such two-phase flows could become rather complex. Obviously, the actual two-phase flow regimes in the SEN are difficult to predict, but, have a distinct influence on the flow pattern and upcoming instabilities in the mould. We present an experimental study concerned with the two-phase flow in a mockup of the continuous casting process of steel. A specific experimental facility was designed and constructed at HZDR for visualizing two-phase flows in the mould and the SEN by means of X-ray radioscopy: the X-LIMMCAST (X-ray LIquid Metal Model of continuous CASTing). This setup utilizes the low melting, eutectic alloy GaInSn as model liquid. The argon gas is injected through the tip of the stopper rod into the liquid metal flow. The system operates continuously under isothermal conditions. First results about the two-phase flow will be presented here accompanied by statistical analysis on the argon bubbles and a discussion of the advantages and limitations of the X-ray method. The position of the X-ray observation window can be changed, which allows the inspection of regions around the gas injection point at the tip of the stopper rod or the development of the bubbly flow in the mould. The X-ray images reveal complex flow situations, for instance, argon bubbles might be attracted by the wall of the SEN near the inlet forming huge bubbles there. Smaller bubbles are generated at the bottom of the SEN, where high shear flows exist. The bubbles in the mould are entrapped by the liquid metal jet. Bubble coalescence can be observed between the bubbles circulating within the flow rolls below the jet. The tendency to rise towards the mould level increases with growing bubble size.
Keywords: continuous casting, liquid metal model, argon injection, two-phase flow, x-ray imaging
  • Lecture (Conference)
    5th International Conference on Modelling and Simulation of Metallurgical Processes in Steelmaking - STEELSIM, 10.-12.09.2013, Ostrava, Tschechische Republik
  • Contribution to proceedings
    5th International Conference on Modelling and Simulation of Metallurgical Processes in Steelmaking - STEELSIM, 10.-12.09.2013, Ostrava, Tschechische Republik

Publ.-Id: 19219 - Permalink

The SRF photo injector at ELBE, status of development and operation
Teichert, J.;
The production of beams with low emittance as well as high average current is one of the key techniques for future electron accelerators and next generation light sources. The superconducting radio-frequency photo electron source (SRF gun) has the potential to fulfill the requirements for these new accelerators. At the radiation source ELBE an SRF gun has been developed and put into operation. The gun has a 3 ½ cell niobium cavity for 1.3 GHz and uses normal-conducting photo cathodes. Since 2010 the gun has delivered beam into the ELBE linac. Recently a new driver laser with 13 MHz pulse repetition rate allows us to operate the IR free-electron lasers (FEL) with the SRF gun. The successful operation of the SRF gun confirms the general design with an elliptical cavity, superconducting RF choke filter, and normal-conducting photocathodes as well as the proper design of most of the subsystems like couplers and tuners. At present, the main draw-back is the low acceleration gradient of the present cavity, and we expect assembly of the new cavity in an improved cryomodule and its commissioning in 2014
Keywords: SRF gun, photo injector, superconducting RF, photo cathode, ELBE, free-electron laser
  • Lecture (others)
    Seminarvortrag, Brookhaven National Laboratory, ATF, 03.09.2013, Upton, USA

Publ.-Id: 19218 - Permalink

Progress of SRF Gun Development and Operation at the ELBE Accelerator
Teichert, J.; Arnold, A.; Buettig, H.; Lehnert, U.; Lu, P.; Michel, P.; Murcek, P.; Schurig, R.; Vennekate, H.; Xiang, R.; Kamps, T.; Rudolph, J.; Kneisel, P.; Will, I.;
Superconducting RF photo guns are suitable candidates for electron injectors in future free-electron lasers and energy recovery linacs. For the radiation source ELBE an SRF gun was build and put into operation. During long-term tests, the operation of normal-conducting photocathodes in the superconducting cavity has been successfully demonstrated. At moderate average currents of some hundreds of μA the Cs2Te photocathodes possess excellent lifetime. The gun's acceleration gradient is the key parameters for beam emittance and the maximum achievable bunch charge of the gun. Therefore two new cavities with higher performance were developed, built and treated. The final tests of these cavities are ongoing. An upgraded cryomodule with an integrated superconducting solenoid was built.
Keywords: SRF gun, superconducting RF, photoinjector, ELBE, Nb cavity
  • Lecture (Conference)
    The 53th ICFA Advanced Beam Dynamic Workshop on Energy Recovery Linacs ERL-2013, 09.-13.09.2013, Novosibirsk, Russia
  • Open Access LogoContribution to proceedings
    The 53th ICFA Advanced Beam Dynamic Workshop on Energy Recovery Linacs ERL-2013, 09.-13.09.2013, Novosibirsk, Russia
    Proceedings of ERL-2013, Novosibirsk, Russia, 2013, Genf: Jacow

Publ.-Id: 19217 - Permalink

Dark Current in Superconducting RF Photoinjectors – Measurements and Mitigation
Teichert, J.; Arnold, A.; Lu, P.; Murcek, P.; Staats, G.; Vennekate, H.; Xiang, R.; Barday, R.; Kamps, T.;
Unwanted beam can cause beam losses and may produce acute or chronic damages of the accelerator. Furthermore it can considerably disturb experiments or increase its back-ground. The operation of the superconducting RF photo gun at the ELBE accelerator has delivered the first experimental information on that topic. It was found, that dark current is an important issue, similar to that of normal conducting RF photo injectors. In the presentation the measurement of dark current, its properties and analysis will be shown and we will discuss ways for mitigation, especially the construction of a dark current kicker.
Keywords: SRF gun, superconducting RF, photo injector, dark current, field emission
  • Lecture (Conference)
    The 53th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs ERL-2013, 09.-13.09.2013, Novosibirsk, Russia
  • Open Access LogoContribution to proceedings
    The 53th ICFA Advanced Beam Dynamic Workshop on Energy Recovery Linacs ERL-2013, 09.-13.09.2013, Novosibirsk, Russia
    Proceedings of ERL-2013, Novosibirsk, Russia, 2013, Genf: Jacow


Publ.-Id: 19216 - Permalink

Bildrekonstruktion für Compton-Kameras zur In-vivo-Dosimetrie in der Ionentherapie
Schöne, S.; Rohling, H.; Enghardt, W.; Fiedler, F.;
Mit Protonen und Ionen lassen sich tumorkonformere Dosisverteilungen als mit Photonen erzielen [1]. Dieser Vorteil erfordert allerdings eine hohe Präzision der Bestrahlung. Um diese zu gewährleisten, ist eine Kontrolle der bei der Bestrahlung applizierten Dosis wünschenswert. Vorgeschlagene Methoden dafür basieren auf Wechselwirkungen von Ionenstrahl und Gewebe: Zum einen werden Positronenemitter gebildet, die durch Partikel-Therapie Positronen-Emissions-Tomographie (PT-PET) die Bildgebung der bei der Bestrahlung erzeugten Aktivität ermöglichen. Zum anderen kommt es zur Emission prompter Gammastrahlung, welche mit Einzelphotonendetektoren gemessen wird (in-beam-SPECT).

PT-PET ist bereits klinisch etabliert. Aufgrund inhärenter physikalischer Beschränkungen ist es bisher nicht möglich, die applizierte Dosis direkt zu messen. In-beam-SPECT unterliegt nicht diesen Limitierungen; aus diesem Grund sollen die Möglichkeiten der Dosiskontrolle mittels der prompten Gammastrahlung evaluiert werden. Neben anderen Methoden [2] ist zur Messung dieser prompten Gammastrahlung die Compton-Kamera vorgeschlagen worden, welche eine „elektronische Kollimation“ nutzt und damit neue Rekonstruktionsmethoden verlangt.

Material und Methoden:
Die Bildrekonstruktion für Compton-Kameras teilt sich in die Aufgaben der Erstellung eines virtuellen Modells der Kamera in Form einer Systemmatrix (SM) und anschließend der Optimierung eines Emissionsbildes, welches möglichst gut zur aufgenommen Messreihe korreliert. Für Letzteres wurde der Standardalgorithmus MLEM (maximum likelihood expectation expectation maximization) [3] in der Derivation LM-MLEM (Listmode-MLEM) [4] verwendet.

Für die aufwändige Erstellung einer realitätsnahen Systemmatrix wurden sowohl – durch die Kinematik der Compton-Streuung bestimmte – grundsätzlich mögliche Herkunftsorte eines Photons, als auch verschiedene Ereigniswahrscheinlichkeiten – bestimmt durch die jeweiligen Wirkungsquerschnitte – berechnet. Da Messungen mit einem physikalischen System zwangsläufig mit Unsicherheiten behaftet sind, handelt es sich bei den Messwerten um Wahrscheinlichkeitsverteilungen. Daher wurden alle Operatoren zur Verarbeitung von Verteilungen entworfen und implementiert. Zur Reduktion des Platz- und Zeitaufwandes wurden Operationen, soweit wie möglich, analytisch statt numerisch gelöst.
Bei MLEM handelt es sich um ein iteratives Verfahren; der Zugriff auf die SM geschieht mehrfach. Da die Erstellzeit der SM den IO-Aufwand zu ihrer persistenten Ablage übersteigt, wurde ein anpassungsfähiger Cachingmechanismus angewandt.

Die genannten Algorithmen wurden auf experimentelle Messreihen und simulierten Daten angewandt.

Die Abbildungen 1 und 2 zeigen beispielhafte Ergebnisse. Abbildung 1 stellt die Rekonstruktion zweier Aufnahmen einer Punktquelle mit dem Prototyp einer Compton-Kamera [5] dar. Die Rekonstruktionen erreichen dabei Genauigkeiten von rund 6 mm bzw. 10 mm Halbwertsbreite für die zentrierte bzw. nicht-zentrierte Quelle. Abbildung 2 zeigt das Resultat der Rekonstruktion einer simulierten Flächenquelle, deren Strukturen bis zu einem gewissen Grad wiederhergestellt werden konnten.

Es ist ersichtlich, dass auch Quellorte außerhalb der Detektorgröße – hier 2² cm² [ebd.] – rekonstruiert werden können.

Es wurde gezeigt, dass mit dem vorgestellten Verfahren die Bildgebung, mittels der für den genannten Anwendungszweck entwickelten Compton-Kamera, grundsätzlich möglich ist. Die erfolgreiche Rekonstruktion des Emissionsbildes konnte sowohl an simulierten, als auch gemessenen Aufnahmen gezeigt werden.
  • Lecture (Conference)
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 18.-21.09.2013, Köln, Deutschland

Publ.-Id: 19215 - Permalink

Dark Current Measurements at the Rossendorf SRF Gun
Xiang, R.; Arnold, A.; Lu, P. N.; Murcek, P.; Teichert, J.; Vennekate, H.; Barday, R.; Kamps, T.; Volkov, V.;
In high gradient photo injectors electron field emission creates so-called dark current. The dark current produces beam loss that increases the radiation level, causes damages to the accelerator components, and produces additional background for the users. Field emitted electrons which stay inside the gun, increases RF power consumption and heat load for the superconducting cavities. It is also believed that dark current is the source of local outgassing and plasma formation which can damage sensitive photocathodes. Thus, to understand and control the dark current has become increasingly important for accelerators. In this presentation, we report on dark current measurement at the ELBE SRF Gun at HZDR. The measurements were carried out with the 3.5 cell-cavity SRF gun and Cs2Te photocathodes. We discuss the dark current behavior for different cavity gradients and various solenoid fields. Simulations have been done to understand the experimental results.
Keywords: SRF gun, superconducting rf, electron injector, dark current, field emission
  • Poster
    FEL 2013, 35th International Free-Electron Laser Conference, 26.-30.08.2013, New York, USA
  • Open Access LogoContribution to proceedings
    FEL 2013, 35th International Free-Electron Laser Conference, 26.-30.08.2013, New York, USA
    Proceedings of FEL 2013, 35th International Free-Electron Laser Conference, New York, USA, 2013: Jacow

Publ.-Id: 19214 - Permalink

Ion-guided microstructure evolution of carbon-nickel nanocomposite films during ion beam assisted deposition: 3D sculpting at the nanoscale
Krause, M.; Buljan, M.; Oates, T. W. H.; Mücklich, A.; Fritzsche, M.; Facsko, S.; Zschornak, M.; Wintz, S.; Endrino, J. L.; Baehtz, C.; Shalimov, A.; Gemming, S.; Abrasonis, G.;
Ion assistance during film growth provides unique opportunities to influence the microstructure due to energy transfer and imposed directionality. For this study, the carbon:nickel system was chosen as model system. The growth of C:Ni nanocomposites without ion assistance is controlled by the phase separation under kinetic constraints of surface and volume diffusion and by the film growth rate. A systematic study of ion irradiation as a pure energy and momentum transfer agent in the context of surface diffusion assisted phase separations is, however, lacking. Here the influence of low energy (50-140 eV) assisting Ar+ ion irradiation on the morphology of C:Ni (~ 5 at.% Ni to ~ 50 at.% Ni) thin films will be reported. Two types of ordered nanostructures are identified and characterized: i) tilted columns and ii) compositionally modulated ripples, which are transferred into a periodic three-dimensional nanoparticle array. For i), the tilt angle and diameter of the nanocolumns are controlled by the deposition parameters. Complex secondary structures like chevrons with partially epitaxial junctions are grown by sequential deposition. For a given composition of the depositing flux, the transition from the columnar growth to the 3D pattern formation regime as a function of the assisting ion energy is demonstrated. The effects of the metal content and the assisting ion current on the self-organized 3D patterns and surface periodicity are studied. The observed microstructures evolution is explained by ion-induced effects.
Keywords: Nanoscale pattern formation, Ion beam assistance, Morphology and microstructure of thin films, Nanocomposites and Nanoparticles
  • Poster
    537th Wilhelm and Else Heraeus Seminar Physics of Ionized and Ion-Assisted PVD: Principles and Current Trends, 26.-28.06.2013, Dresden, Deutschland

Publ.-Id: 19213 - Permalink

FEL Operation with the superconducting RF photo gun at ELBE
Teichert, J.; Arnold, A.; Büttig, H.; Justus, M.; Lehnert, U.; Lu, P. N.; Michel, P.; Murcek, P.; Schurig, R.; Seidel, W.; Vennekate, H.; Xiang, R.; Kamps, T.; Rudolph, J.; Will, I.;
The superconducting RF photoinjector (SRF gun) operating with a 31/2-cell niobium cavity and Cs2Te photocathodes is installed at the ELBE radiation center. The gun provides beams for ELBE as well as in a separate diagnostics beam line for beam parameter measurements. Since 2012 a new UV driver laser system developed by MBI has been installed for the SRF gun. It delivers CW or burstmode pulses with 13MHz repetition rate or with reduced rates of 500, 200, and 100 kHz at an average UV power of about 1W. The new laser allows the gun to serve as the driver for the infrared FELs at ELBE. In the first successful experiment a 260 µA beam with 3.3 MeV from SRF gun was injected into ELBE, further accelerated in the ELBE superconducting linac modules and then guided to the U100 undulator. First lasing was achieved at the wavelength of 41 µm. The spectrum, detuning curve and further parameters were measured.
Keywords: photoinjector, superconducting rf, free-electron laser, srf gun
  • Lecture (Conference)
    FEL2013, 35th International Free-Electron Laser Conference, 26.-30.08.2013, New York, USA
  • Poster
    FEL 2013, 35th International Free-Electron Laser Conference, 26.-30.08.2013, New York, USA
  • Open Access LogoContribution to proceedings
    FEL 2013, 35th International Free-Electron Laser Conference, 26.-30.08.2013, New York, USA
    Proceedings of 35th International Free-Electron Laser Conference, New York, USA, 2013, Genf: Jacow


Publ.-Id: 19212 - Permalink

Simultaneous STXM imaging and resistance measurements of trilayer vortices
Banholzer, A.; Wintz, S.; Fowley, C.; Deac, A.; Raabe, J.; Lenz, K.; Lindner, J.; Fassbender, J.ORC
We investigate a trilayer vortex system by simultaneous scanning transmission X-ray microscopy (STXM) and in-situ giant magnetoresistance (GMR) measurements. Our aim is to correlate the magnetic configuration of both magnetic layers with the corresponding magneto-resistance effects.
The sample is a Co/Cu/Ni80Fe20 cylindrical trilayer, with 2 µm diameter [1]. Top and bottom contacts allow to apply a perpendicular DC current to measure the resistance. Simultaneously the magnetic configuration of each element of the disc is imaged using STXM. This is performed at the Paul Scherrer Institute. The vortex core formation in both magnetic layers and the position of the vortex core can be controlled by applying an in-plane external magnetic field. When the cores are at the edge, and the magnetization state resembles that of two in-plane magnetized disks, the GMR is low, as both cores move towards the center. With decreasing field the resistance increases, as the cores move beyond the center and towards the opposite side, the resistance decreases again. We investigate the resistance at different DC currents in dependency on the swept magnetic fields.
[1] S. Wintz, Appl. Phys. Lett. 98, 232511 (2011)
Keywords: Vortex, STXM
  • Lecture (Conference)
    Joint European Magnetic Symposia (JEMS) 2013, 25.-30.08.2013, Rhodos, Greece

Publ.-Id: 19211 - Permalink

Direct Condensation and Entrainment Installation for Steam Experiments TOPFLOW-DENISE: Stratified Steam Condensation Experiments
Seidel, T.; Beyer, M.;
In a hypothetical Small Break Loss of Coolant Accident (SB-LOCA) in a Pressurized Water Reactor (PWR), the Reactor Pressure Vessel wall (RPV) may be exposed to thermal stress, since Emergency Core Cooling Systems (ECCS) injects cold water. The loads on the primary loop and RPV walls are determined by mixing processes with the surrounding hot water and by the condensation of steam on the surface (see Bestion 2010 and Lucas 2005)
For the development and validation of CFD-models, experiments have to meet a high standard of reproducibility, measurement certainty and temporal and local resolution. The pressure tank technology of the TOPFLOW facility allows conducting such experiments at reasonable effort.
The Direct Condensation and Entrainment Installation for Steam Experiments (DENISE) is made for CFD-grade condensation experiments at up to 50 bars pressure (see Figure 1). Subcooled water is injected into the DENISE-basin in three different configurations for experimental investigation:
A) Stratified flow
B) Subcooled water Jet
C) steam bubble entrainment with a jet falling on a stratified surface
The experimental facility is equipped with a dense instrumentation. The flow inside is observed and controlled with a high speed camera and an infrared camera, coriolis flow meters and a set of micro thermocouples. The facility is supplied with a 4 MW electrical boiler, saturated water pumps, a 30 kW electrical heater and a 2 MW water cooler.
The first series contains stratified flow experiments comparable to non-adiabatic flow inside hot and cold legs of PWRs. Measurement results can be compared to CFD simulations. Recently 56 experiments have been carried out according to the test matrix in Table 1.
The observed high speed and infrared images from the reference experiment are shown in Figure 2. The surface is slightly wavy and a small increase of water temperature is observable between inlet (left) and outlet (right). Processed data from these measurements, like the temperature plots shown in Figure 3 will provide comparable results for the development and validation of CFD-models.
Experiments with stratified steam-water surfaces have been carried out in August 2013. They are being analyzed till end of 2013. For the next experiments, a jet injector will be added to the facility and plunging jet experiments with bubble entrainment will be measured. Finally, there will be experiments with a subcooled water jet falling through the steam atmosphere. A special movable thermo sensor will be used to measure temperature profiles inside the jet.
  • Lecture (Conference)
    150 Jahre - Richard Mollier, Internationales Kolloquium zum 150. Geburtstag von Richard Mollier, 21.-23.11.2013, Dresden, Germany

Publ.-Id: 19210 - Permalink

Lateral spin transfer torque induced magnetic switching at room temperature demonstrated by x-ray microscopy.
Buhl, M.; Erbe, A.; Grebing, J.; Wintz, S.; Raabe, J.; Fassbender, J.ORC
Changing and detecting the orientation of nanomagnetic structures, which can be used for durable information storage, needs to be developed towards true nanoscale dimensions for keeping up the miniaturization speed of modern nanoelectronic compo- nents. Therefore, new concepts for controlling the state of nanomagnets are currently in the focus of research in the field of nanoelectronics. Here, we demonstrate re- producible switching of a purely metallic nanopillar placed on a lead that conducts a spin-polarized current at room temperature. Spin diffusion across the metal-metal (Cu to CoFe) interface between the pillar and the lead causes spin accumulation in the pillar, which may then be used to set the magnetic orientation of the pillar. In our experiments, the detection of the magnetic state of the nanopillar is performed by direct imaging via scanning transmission x-ray microscopy (STXM).
Keywords: Magnetic Materials and Devices, Nanosensors and other Devices, Surface Patterning and Imaging

Publ.-Id: 19209 - Permalink

Entwicklung von CFD-Modellen für Wandsieden und Entwicklung hochauflösender, schneller Röntgentomographie für die Analyse von Zweiphasenströmungen in Brennstabbündeln
Krepper, E.; Rzehak, R.; Barthel, F.; Franz, R.; Hampel, U.;
In einem Verbundprojekt im Rahmen des Programms „Energie 2020+“ gefördert durch das BMBF koordiniert durch das HZDR arbeiteten 4 Universitäten, 2 Forschungszentren und ANSYS zusammen. Der vorliegende Bericht beschreibt die Arbeiten des HZDR, die im Zeitraum September 2009 bis Januar 2013 durchgeführt wurden. Das Vorhaben war auf die Entwicklung und Validierung von CFD-Modellen von unterkühltem Sieden bis zu Filmsieden gerichtet.
Im Bericht werden die entwickelten und verwendeten Modelle dargestellt. Anhand der Nachanalyse von Experimenten wird auf die vorgeschlagene Kalibrierung der Modelle eingegangen. Wichtig ist hierbei eine genauere Beschreibung der Zwischenphasengrenzfläche, die durch Kopplung des Wandsiedemodells mit einem Populationsmodell erreicht werden kann. Anhand der Analyse von Bündelexperimenten konnte gezeigt werden, dass die gemessenen querschnittsgemittelten Messwerte mit einem Satz im Rahmen der Modellunsicherheiten kalibrierter Modellparameter reproduziert werden kann. Für die Berechnung der Verteilungsmuster des Dampfgehaltes im Kanalquerschnitt muss die Modellierung der Turbulenz beachtet werden.
Die experimentellen Arbeiten waren auf die Untersuchung eines Brennelementbündels gerichtet. An einer Versuchsanordnung zu einem Brennelementbündel werden die turbulente einphasige Geschwindigkeit (PIV), der mittlere Gasgehalt (Gamma-Densitometrie) sowie der zeitlich und räumlich aufgelöste Gasgehalt (Hochgeschwindigkeits-Röntgentomographie) gemessen. Letztere Methode wurde in Rossendorf entwickelt.
Keywords: boiling, CFD, bubbly flow, momentum exchange, mass exchange, population balance model, experiments, PIV, gamma densitometry, fast x-ray tomography
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-040 2013
    ISSN: 2191-8708


Publ.-Id: 19208 - Permalink

Laser assisted Compton scattering of X-ray photons
Seipt, D.; Kämpfer, B.;
The Compton scattering of X-ray photons, assisted by a short intense optical laser pulse is discussed. The differential scattering cross section reveals the interesting feature that the main Klein-Nishina line is accompanied by a series of side-lines forming a broad plateau where up to ${\cal O} (10^3)$ laser photons participate simultaneously in a single scattering event. Due to the non-linear mixing of X-ray and laser photons a frequency dependent rotation of the polarization of the final state photons relative to the scattering plane emerges. A consistent description of the scattering process with short laser pulses requires to work with X-ray pulses. An experimental investigation can be accomplished, e.g., at LCLS or the European XFEL in the near future.

Publ.-Id: 19207 - Permalink

Magnetic properties of granular CoCrPt:SiO2 thin films deposited on GaSb nanocones
Ball, D. K.; Lenz, K.; Fritzsche, M.; Varvaro, G.; Günther, S.; Krone, P.; Makarov, D.; Mücklich, A.; Facsko, S.; Fassbender, J.ORC; Albrecht, M.
We report on the effect of microstructure on the magnetic properties of granular CoCrPt:SiO2 films with weakly interacting magnetic grains deposited on pre-structured GaSb nanocone templates fabricated by ion erosion technique. By tuning the irradiation conditions, nanocone patterns of different cone size were prepared (from 28 to 120 nm in diameter and 32 to 330 nm high, respectively). The influence of the intergranular exchange coupling was also investigated by varying the SiO2 content from 8 to 12 at.\%. Deposition of CoCrPt:SiO2 on samples with small nanocones leads to a close magnetic grain packing, which results in the formation of extended magnetic domains larger than the average distance between the GaSb cones. In contrast, on larger nanocones, the magnetic coating grows on the side-walls with large separation between neighbouring cones leading to magnetic single-domain regions, which are correlated to the underlying structure. Magnetometry measurements indicate that both remanence and coercivity decrease with increasing cone size and/or SiO2 content due to the combined effect of the angular distribution of the magnetic easy axis of the grains and the intergranular exchange coupling strength.
Keywords: Magnetic granular films, Ion beam erosion, nanocones

Publ.-Id: 19206 - Permalink

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