Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32228 Publications
Networks of silicon nanowires: a large-scale atomistic electronic structure analysis
Keles, U.; Liedke, B.; Heinig, K.-H.; Bulutay, C.;
Networks of silicon nanowires possess intriguing electronic properties surpassing the predictions based on quantum confinement of individual nanowires. Employing large-scale atomistic pseudopotential computations, as yet unexplored branched nanostructures are investigated in the subsystem level, as well as in full assembly. The end product is a simple but versatile expression for the bandgap and band edge alignments of multiply-crossing Si nanowires for various diameter, number of crossings, and wire orientations. Further progress along this line can potentially topple the bottom-up approach for Si nanowire networks to a top-down design by starting with functionality and leading to an enabling structure.
Keywords: nanowire networks, branched nanowires, nanoscale silicon, electronic structure

Publ.-Id: 19330 - Permalink


Fission Experiments at nELBE
Kögler, T.; Beyer, R.; Hannaske, R.; Junghans, A. R.; Massarczyk, R.; Wagner, A.;
A 235U and a 242Pu parallel-plate fission ionization chamber will be used to investigate fast neutron-induced fission cross sections at the Center for High-Power Radiation Sources at Helmholtz-Zentrum Dresden-Rossendorf. To optimize the chamber parameters extensive Geant4 simulations with GEF code generated fission observable inputs have been used. Pile-up effects had to be included due to the high α-activity of the plutonium targets. For the determination of targets surface density and homogeneity an α-spectroscopy setup was developed and simulations related to that will also be presented.
Keywords: Neutron-induced fission cross sections; Stopping power of fission fragments using Geant4; Minor actinide target characterization; nELBE
  • Lecture (Conference)
    Scientific Workshop on Nuclear Fission Dynamics and the Emission of Prompt Neutrons and Gamma Rays, 28.-30.11.2012, Biarritz, France
  • Open Access LogoPhysics Procedia 47(2013), 178-183
    DOI: 10.1016/j.phpro.2013.06.026

Publ.-Id: 19329 - Permalink


Toward nonconventional human–machine interfaces for supervisory plant process monitoring
Skripcak, T.; Tanuska, P.; Konrad, U.; Schmeisser, N.;
This paper describes a novel methodology for designing alternative human–machine interfaces (HMI) dealing with the industrial process control visualization and plant monitoring. The system is based on a multiagent approach in order to allow visualizations using nonconventional display devices (e.g., power-wall or table) combined with the natural user interaction (NUI) paradigm. This type of HMI solution could form an optional extension to current systems employed in a plant monitoring. Namely the utilization of a virtual reality creates new opportunities for the HMI system use cases, where an enhanced visualization and interaction can improve decision making strategies in complex processes. An immersive plant personnel training or realistic process visualizations are examples where the usage of the third dimension can be helpful. Nevertheless, the development of nonconventional HMI increases the complexity of the industrial information system environment. The question is how to adapt the system design for the nonconventional HMI, in a contrast with the conventional solutions. We applied the multiagent approach, which leads to a more robust and less-coupled component structure. An experimental prototype was implemented on the top of the proposed methodology. A simulation of an absorption refrigeration process was used as a process model on top of which the prototype was designed. Interoperability was gained via the automation standard of OPC UA. Furthermore, in order to optimize our NUI agent, a user testing application was developed for the evaluation of exploratory interaction tasks in a power-wall display scenario. The proposed framework provides fundamental guidelines for designing and developing a new generation of HMI systems.
Keywords: Human–machine interfaces; natural user interaction; nonconventional displays; virtual factory; virtual reality

Publ.-Id: 19328 - Permalink


Status of the Development of a Single γ -ray Imaging System for in-vivo Dosimetry at Particle Beams
Schoene, S.; Enghardt, W.; Golnik, C.; Hueso-Gonzalez, F.; Kormoll, T.; Mueller, A.; Pausch, G.; Petzoldt, J.; Rohling, H.; Roemer, K.; Fiedler, F.;
Ion beams offer advantages over conventional treatment modalities, such as photons. Because of the way ions deposit their energy on their path through tissue they allow for an increased dose deposition in the tumor volume and reduce the collateral damage to the surrounding healthy tissue. However, small changes in the irradiated volume will lead to a misalignment of the deposited dose maximum and the tumor. Therefore, a dose monitoring system is highly desirable. Positron Emission Tomography (PET) was clinically applied for example between 1997 and 2008 at the GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt, Germany, for monitoring the dose delivered by 12-C beams. Due to inherent limitations of this method, a direct quantification of the delivered dose is not feasible. Therefore, another approach currently under investigation monitors the dose by means of the detection of prompt $\gamma$-rays. A Compton camera may be a feasible technical solution for such a monitoring system. To set up a clinical monitoring system a comprehensive simulation of the creation of secondary radiation as well as of the detection process is required. Furthermore, a sophisticated reconstruction of the data is essential. This paper will show the capability of the reconstruction to image also events measured by means of a Compton camera gamma-rays having energies of 4.4 MeV.
  • Poster
    Nuclear Science Symposium and Medical Imaging Conference, 27.10.-02.11.2013, Seoul, Republik Korea
  • Poster
    Workshop on Range Assessment and Dose Verification in Particle Therapy, 29.-30.09.2014, Dresden, Deutschland

Publ.-Id: 19327 - Permalink


Modeling and Analysis of Compositional Data
Pawlowsky-Glahn, V.; Egozcue, J. J.; Tolosana-Delgado, R.;
These notes have been prepared as support to a short course on compositional data analysis. The first version dates back to the year 2000. Their aim is to transmit the basic concepts and skills for simple applications, thus setting the premises for more advanced projects. The awareness of problems related to the statistical analysis of compositional data analysis dates back to a paper by Karl Pearson (1897), which title began significantly with the words "On a form of spurious correlation". The aim of these notes is to summarize the last stages of research on this topic, focusing on the practical aspects necessary for a statistical modelling of these kind of data. The notes are based both on the monograph by John Aitchison, "Statistical analysis of compositional data" (1986), and on recent developments that complement the theory developed there. These notes have been updated over the years, and frequent updates will be still required in the near future, as the theory presented here is a field of active research.
Keywords: compositions, proportions, logratio approach, isometric logratio, centered logratio, additive logratio, log-ratio, Aitchison geometry, perturbation, simplex, sample space, scale.
  • Book (Authorship)
    London: WIley, 2015
    247 Seiten

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Publ.-Id: 19326 - Permalink


Microbial influence on the immobilization of radionuclides in crystalline rock environments
Krawczyk-Bärsch, E.;
In crystalline rock, the dominant transport medium for radionuclides is groundwater flowing through subsurface fractures. Since groundwater is containing microorganisms, fracture surfaces support biological growth of microbial communities. The formed subsurface microbial communities have a significant effect on the adsorption capacity of host rock formations by forming a barrier between the rock surface and the groundwater. But how do these microbial communities influence the mobilization or immobilization of radionuclides in the case of a nuclear incident? As known from experiments performed on biofilms from the underground rock characterization facility tunnel ONKALO in Finland and from the Äspö Hard Rock Laboratory (HRL) in Sweden, microbes can significantly affect subsurface biogeochemical interactions, leading to the immobilization and (bio-)adsorption of radionuclides. Under the ambient conditions in the Äspö HRL (neutral pH of the groundwater, high amount of ferrous iron in the groundwater, aerobic conditions) the uptake of radionuclides like U(VI) and Np(V) was determined to be 85% and 95%, respectively due to the abundant surface area of the bacteriogenically formed ferrihydrite.

In order to define the influence of microbial communities and their relevance in the safety assessment of a nuclear waste repository some important points have to be considered;
- We have to characterize the possible microbial diversity during changing geochemical conditions (Eh, pH, T, p, chemical composition of the groundwater) in an opened and closed deposit. Bioaccumulation experiments performed on selected microbes using different radionuclides have to emphasize at least on aerobic conditions.
- Information about the sources for electron donors and electron acceptors for microbial activity are needed.
- To estimate the relevance of microbial process, we have to know more about the kinetic of microbial growth. Therefor we have to trace the effect of microbial metabolism and growth in a geochemical system using a generalized kinetic rate law. We need to estimate biofilm growth for process description, including different scales and different types of radionuclides. What are the parameters, which are needed for modeling the kinetic of microbial growth? The aim of the modeling will be a quantification of microbial processes and the assessment of microbially mediated retention of radionuclides.
Keywords: Uranium, rock formation, biofilm
  • Lecture (others)
    IGD-TP 4th Exchange Forum, 29.-30.10.2013, Prag, Tschechische Republik

Publ.-Id: 19325 - Permalink


Immobilization of uranium and neptunium by microorganisms in subsurface crystalline rock environments
Krawczyk-Bärsch, E.; Pedersen, K.; Lehtinen, A.; Arnold, T.; Schmeide, K.;
In crystalline rock, the dominant transport medium for radionuclides is groundwater flowing through subsurface fractures. Since groundwater is containing microorganisms, fracture surfaces support biological growth of microbial communities, the so-called biofilms. The microbial diversity of these biofilms depends on the microbial consortia and the chemical composition of the fracture water. Subsurface biofilms have a significant effect on the adsorption capacity of host rock formations by forming a barrier between the rock surface and the groundwater. They can significantly affect subsurface biogeochemical interactions, leading to the immobilization and adsorption of radionuclides.

Microbial studies were performed to evaluate the relevance of microbial processes for the immobilization of radionuclides in a deep crystalline repository for high-level radioactive waste. Studies were performed in Olkiluoto, in the underground rock characterisation facility ONKALO in Finland, and in the Äspö Hard Rock Laboratory (HRL) in Sweden.
Massive 5–10-mm thick biofilms were observed in both sites attached to tunnel walls where groundwater was seeping from bedrock fractures. In experiments the effect of uranium on biofilms was studied on site in the ONKALO tunnel by adding UO2(ClO4)2 with a final U-concentration of 1.0×10-5 M to the fracture water in a self constructed flow cell by using detached biofilm samples. Biofilm specimens collected for transmission electron microscopy studies indicated that uranium in the biofilm was immobilized intracellularly in microorganisms as needle-shaped uranyl phosphate minerals, similar to meta-Autunite (Ca[UO2]2[PO4]2•10-12H2O). In contrast, thermodynamic calculation of the theoretical predominant fields of uranium species and time-resolved laser fluorescence spectroscopy showed that the formation of aqueous uranium carbonate species Ca2UO2(CO3)3 and Mg2UO2(CO3)3 was predicted due to the high concentration of carbonate in the groundwater.
At the Äspö HRL (Sweden) Gallionella ferruginea dominated biofilms associated with bacteriogenic iron oxides (BIOS) and groundwater were sampled from an in situ continuous flow cell, which has been installed in a cavity of the main access tunnel. In laboratory sorption experiments UO2(ClO4)2 and NpO2ClO4 were added to the BIOS biofilms in groundwater under aerobic conditions adjusting a final U(VI) concentration of 1.9×10-5 M.U(VI) and 3.27×10-5 M Np(V). The results of the experiments showed that in the BIOS biofilm the ferrous iron-oxidizing and stalk-forming bacterium Gallionella ferruginea is dominating the sorption process. The stalk represents an organic surface upon which Fe oxyhydroxides can precipitate. Under the given pH conditions the uptake of uranium (85%) and Np (95%) depends predominantly on the high amount of ferrihydrite precipitated onto the stalks. The results showed that the combination of the biological material and Fe oxides created an abundant surface area for bioaccumulation and adsorption of radionuclides.
Keywords: Uranium, Biofilm
  • Contribution to proceedings
    International Conference on Radioecology & Environmental Radioactivity, 07.-12.09.2014, Barcelona, Spain
  • Poster
    International Conference on Radioecology & Environmental Radioactivity,, 07.-12.09.2014, Barcelona, Spain

Publ.-Id: 19324 - Permalink


Searching a Dark Photon with HADES
Agakishiev, G.; Balanda, A.; Belver, D.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Chernenko, S.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Göbel, K.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kornakov, G.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.;
We present a search for the e+e- decay of a dark photon, also known as U vector boson, in inclusive dielectron spectra measured by HADES in the 3.5 GeV p+p and p+Nb reactions, as well as the 1.756 GeV/u Ar+KCl reaction. An upper limit on the kinetic mixing parameter squared ε2 at 90% CL has been obtained for the mass range MU = 0.02 - 0.55 GeV/c2 and is compared with the present world data set. For masses 0.03 - 0.1 GeV/c2, the limit has been lowered with respect to previous results, allowing now to exclude a large part of the parameter region favoured by the muon g -2 anomaly. Furthermore, an improved upper limit of 2.3x10-6 has been set on the helicity-suppressed direct decay of the eta meson, η-> e+e-, at 90% CL.

Publ.-Id: 19323 - Permalink


An upper limit on hypertriton production in collisions of Ar(1.76A GeV)+KCl
Agakishiev, G.; Belver, D.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Castro, E.; Chernenko, S.; Destefanis, M.; Dohrmann, F.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Lang, S.; Lange, J. S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Moriniere, E.; Mousa, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmah, A.; Schuldes, H.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wendisch, C.; Wisniowski, M.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.;
A high-statistic data sample of Ar(1.76 AGeV)+KCl events recorded with HADES is used to search for a hypertriton signal. An upper production limit per centrality-triggered event of 1.04 x10-3 on the 3σ level is derived. Comparing this value with the number of successfully reconstructed Λ hyperons allows to determine an upper limit on the ratio N3HΛ/NΛ, which is confronted with statistical and coalescence-type model calculations.

Publ.-Id: 19322 - Permalink


Uranium(VI) Chemistry in Strong Alkaline Solution: Speciation and Oxygen Exchange Mechanism
Moll, H.; Rossberg, A.; Steudtner, R.; Drobot, B.; Müller, K.; Tsushima, S.;
The mechanism by which oxygen bound in UO22+ exchanges with that from water under strong alkaline conditions remains a subject of controversy. Two recent NMR studies independently revealed that the key intermediate species is a binuclear uranyl(VI) hydroxide, presumably of the stoichiometry [(UO2(OH)42−)(UO2(OH)53−)]. The presence of UO2(OH)53− in highly alkaline solution was postulated in earlier experimental studies, yet the species has been little characterized. Quantum-chemical calculations (DFT and MP2) show that hydrolysis of UO2(OH)42− yields UO3(OH)33− preferentially over UO2(OH)53−. X-ray absorption spectroscopy was used to study the uranium(VI) speciation in a highly alkaline solution supporting the existence of a species with three U−O bonds, as expected for UO3(OH)33−. Therefore, we explored the oxygen exchange pathway through the binuclear adduct [(UO2(OH)42−)(UO3(OH)33−)] by quantum-chemical calculations. Assuming that the rate-dominating step is proton transfer between the oxygen atoms, the activation Gibbs energy for the intramolecular proton transfer within [(UO2(OH)42−)(UO3(OH)33−)] at the B3LYP level was estimated to be 64.7 kJ mol−1. This value is in good agreement with the activation energy for “yl”−oxygen exchange in [(UO2(OH)42−)(UO2(OH)53−)] obtained from experiment by Szabó and Grenthe (Inorg. Chem. 2010, 49, 4928−4933), which is 60.8 ± 2.4 kJ mol−1. Both the presence of UO3(OH)33− and the scenario of an “yl”−oxygen exchange through a binuclear species in strong alkaline solution are supported by the present study.

Publ.-Id: 19321 - Permalink


Estimation of Parameters in Random Dynamical Systems
Konsulke, S.; van den Boogaart, K. G.; Ballani, F.; Franke, M.; Sauke, M.;
In random dynamical systems, e.g. described by stochastic differential equations, it is often difficult to infer the parameters. The main difficulty is that one hand no likelihoods can be computed, excluding Maximum Likelihood, EM or Bayesian Methods and on the other hand the system is random, excluding simple least squares comparison of the observations with expected trajectories of the dynamical system. We have developed a new R-package ”SysStat” containing general approaches for estimation in stochastic systems based on simulation rather than likelihood computation using approximate Bayes and approximate quasi-likelihood methods finding good approximations based on informed user choices and simulations of the models with varying parameters. The user choice especially includes finding functions of the data with high information contend in the sense of high quasi-likelihood. Although both methods are not directly applicable to dynamic systems, there are systematic ways of constructing such informative statistics for stochastic differential equation models, allowing to construct informative functions for the local dynamic and translating these functions to informative statistics of the global dynamic by time averaging. This allows to estimate parameters of dynamic stochastic models efficiently. Our main aim is the modeling of bioleaching processes, but the method has a more general applicability for various types of processes in the geosciences including stationary and transient, spatial, temporal and spatiotemporal processes and will thus be demonstrated with simple to understand toy examples.
Keywords: Parameter estimation, dynamical systems, nonlinear methods
  • Contribution to proceedings
    15th Annual Conference of the International Association for Mathematical Geosciences, 02.-06.09.2013, Madrid, Spanien
    Mathematics of Planet Earth - Proceedings of the 15th Annual Conference of the International Association for Mathematical Geosciences: Springer, 978-3-642-32407-9, 843-846
    DOI: 10.1007/978-3-642-32408-6_183
  • Lecture (Conference)
    15th Annual Conference of the International Association for Mathematical Geosciences, 03.09.2013, Madrid, Spanien

Publ.-Id: 19320 - Permalink


Evaluierung F-18-markierter Fluspidin-Enantiomere: Spezifische Eignung für die molekulare Bildgebung von Sigma-1-Rezeptoren
Deuther-Conrad, W.; Becker, G.; Patt, M.; Donat, C. K.; Maisonial-Besset, A.; Funke, U.; Holl, K.; Fischer, S.; Hiller, A.; Wenzel, B.; Steinbach, J.; Sabri, O.; Wünsch, B.; Brust, P.;
Ziel: Sigma-1-Rezeptoren (S1R) regulieren eine Vielzahl physiologischer Prozesse. Störungen in den S1R-vermittelten Signalkaskaden werden mit Hirn-, Herz-, und Krebserkrankungen in Verbindung gebracht. Die PET-basierte Validierung von S1R als Biomarker und Zielstruktur für neuartige Therapiekonzepte ist somit von hohem Interesse. Wir haben mit (S)-F-18-Fluspidin und (R)-F-18-Fluspidin S1R-spezifische Radiotracer entwickelt, deren Eignung für die In-vivo-Bildgebung von S1R zu evaluieren ist.

Methodik: Die beiden Radiotracer wurden ausgehend von den enantiomerenreinen Tosylat-Präkursoren in einem automatisierten Prozess synthetisiert. Die Pharmakokinetik der Hirnaufnahme wurden mittels dynamischer PET Studien unter Kontrollbedingungen (n=3/Enantiomer) und bei S1R-Blockade (SA4503, n=3/Enantiomer) an Ferkeln untersucht. Zeit-SUV-Daten wurden für 24 Hirnregionen ermittelt. Die kinetische Modellierung und Berechnung der Verteilungsvolumina (VD) erfolgte nicht-linear (1-, 2-Kompartiment-Modell) und durch graphische Linearisierung (Logan plot).

Ergebnisse: (S)- und (R)-F-18-Fluspidin wurden mit hoher spezifischer Aktivität (710 ± 424 GBq/µmol) synthetisiert. Die initial gemessene Hirnaufnahme beider Radiotracer ist vergleichbar. Zu späten Untersuchungszeiten wurden für das (R)-F-18-Fluspidin signifikant höhere Werte für SUV ermittelt. S1R-Inhibition reduziert in allen Hirnregionen SUV und den Rezeptorbindungsparameter k3 beider Radiotracer signifikant um ~65% bzw. 70-90%. Die mit Logan plot ermittelten VD-Werte sind unter S1R-Blockade ebenfalls signifikant vermindert und korrelieren unter Kontroll- und Blockadebedingungen mit den durch nicht-lineare Analyse ermittelten VD-Werten.

Schlussfolgerungen: Mit (S)-F-18-Fluspidin und (R)-F-18-Fluspidin liegen zwei S1R-spezifische Radiotracer vor, die aufgrund ihrer verschiedenen Pharmakokinetik für die diagnostische und therapiebegleitende Bildgebung unterschiedlicher Krankheitsprozesse geeignet sein könnten.
  • Lecture (Conference)
    NuklearMedizin2014, 26.-29.03.2014, Hannover, Deutschland
  • Open Access LogoAbstract in refereed journal
    Nuklearmedizin 53(2014), A43

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Publ.-Id: 19319 - Permalink


The IR and THz user facility FELBE
Seidel, W.;
The FELBE user facility located at the Helmhotz-Zentrum Dresden-Rossendorf operates two free-electron lasers (FELs). Here we discuss the basic parameters of the FELs and the experimental opportunities at the facility. The FELs are based on the superconducting electron linear accelerator ELBE, which provides short (picosecond) electron bunches with energies up to 35 MeV at a 13 MHz repetition rate. The two FELs of FELBE (FELBE stands for FEL@ELBE) are equipped with two undulators, one for the mid-infrared spectral range (wavelengths 4 – 21 µm) and one for the far-infrared or THz range (wavelengths 18 – 250 µm).
The key feature which distinguishes FELBE from other FEL user facilities is the possibility of “quasi cw” operation (meaning a continuous train of pulses, also called micropulses), made possible by the superconducting accelerator cavities. The FEL thus provides picosecond optical pulses at a repetition rate of 13 MHz. In this mode, the average power can reach up to 30 W (depending on the wavelength) corresponding to more than 1 µJ pulse energy. Additionally FELBE can be operated in a macrobunch mode and, via pulse-picking, a 1 kHz mode.
The two FELs can be synchronized to a number of tabletop femtosecond and picosecond lasers, enabling two-color experiments from the near-infrared to the THz frequency range. The main techniques at FELBE are pump-probe spectroscopy [1-3] and time-resolved photoluminescence [4]. Furthermore there is a lab devoted to near-field microscopy [5]. Spectroscopy with FELBE radiation is also possible in pulsed high magnetic fields up to 70 T (150 ms magnetic pulse duration) [6].
At the ELBE accelerator a new electron beamline, providing for femtosecond electron bunches with up to nC bunch charges and repetition rates in the 1-200 kHz regime has been constructed and is corrently tested. The electrons will be used for the generation of broad band and narrow bandwidth coherent THz pulses in the frequency range between 0.1 THz – 3 THz. The current status of this project is presented.
FELBE is operated as a user facility, i.e., scientists from other institutions are invited to submit short research proposals and apply for beamtime.

References

[1] D. Stehr et al., Appl. Phys. Lett. 92, 051104 (2008).
[2] E.A. Zibik, et al., Nature Mat. 8, 803 (2009).
[3] S. Winnerl et al., Phys. Rev. Lett. 107, 237401 (2011).
[4] J. Bhattacharyya et al., Rev. Sci. Instr. 82, 103107 (2011).
[5] S.C. Kehr et al., Nature Comm. 2, 249 (2011).
[6] O. Drachenko et al., Phys. Rev. B 79, 073301 (2009).
  • Invited lecture (Conferences)
    Turkish Accelerator Center 3rd Light Sources User's Meeting (TAC-LSUM 2013), 05.-07.10.2013, Ankara, Turkey

Publ.-Id: 19318 - Permalink


Synthesis, Characterization, and Metabolism Studies of Fluspidine Enantiomers
Holl, K.; Falck, E.; Köhler, J.; Schepmann, D.; Humpf, H.-U.; Brust, P.; Wünsch, B.;
The enantiomers of the potent σ1 ligand fluspidine (1) were prepared by using chiral preparative HPLC. Synthesis of racemic tosylate 2 and subsequent separation of enantiomers yielded (R)-2 and (S)-2 in excellent enantiomeric purities. The fluspidine enantiomers (R)-1 and (S)-1 were synthesized from (R)-2 and (S)-2 by nucleophilic substitution with tetra-n-butyl-ammonium fluoride, affording (R)-1 with 99.6% ee and (S)-1 with 96.4% ee. Tosylates (R)-2 and (S)-2 can also serve as precursors for the radiosynthesis of enantiomerically pure radiotracers [18F](R)-1 and [18F](S)-1. The absolute configuration of the pure enantiomers was elucidated by comparison of their CD spectra with a calculated CD spectrum of a simplified model compound. In receptor binding studies, both enantiomers displayed very high σ1 receptor affiniy and selectivity against the σ2 receptor. (R)-Fluspidine ((R)-1) is the eutomer, with a K1 value of 0.57 nM and a eudysmic ratio of 4. Incubation of (R)-1 and (S)-1 with rat liver microsomes led to the identification of seven and eight metaboites, respectively. Although the S-configured enantiomer formed additional metabolite (S)-1-3, it ist metabolically more stable than (R)-1.

Publ.-Id: 19317 - Permalink


Near-infrared extension of a visible spectrum airborne sun photometer
Starace, M.; von Bismarck, J.; Hollstein, A.; Ruhtz, T.; Preusker, R.; Fischer, J.;
The continuously-measuring, multispectral airborne Sun and aureole photometers FUBISS-ASA and FUBISSASA2 were developed at the Institute for Space Sciences of the Freie Universität Berlin in 2002 and 2006 respectively, for the retrieval of aerosol optical and microphysical parameters at wavelengths ranging from 400 to 900 nm. A multispectral near-infrared direct sun radiometer measuring in a spectral range of 1000 to 1700 nm has now been added to FUBISS-ASA2. The main objective of this NIR extension is to enhance the characterization of larger aerosol particles, as Mie scattering theory offers a more accurate approximation for their interaction with electromagnetic radiation, if both the VIS and NIR parts of the spectrum are considered, than it does for the VIS part only. The spectral transmissivity of atmospheric models was computed using the HITRAN2008 database in order to determine local absorption minima suitable for aerosol retrieval. Measurements were first carried out aboard the research vessel FS Polarstern on its transatlantic voyage ANT-XXVI/1. Additional measurements were performed from the Sphinx High Altitude Research Station on the Jungfraujoch and in the nearby Kleine Scheidegg locality during the CLACE2010 measurement campaign. Aerosol optical parameters derived from VIS aureole and direct sun measurements were compared to those of simulated aerosol mixtures in order to estimate the composition of the measured aerosol.
Keywords: FUBISS, ASA2, Multispectral, Aureole, Sunphotometer, Aerosol, Remote sensing
  • Open Access LogoContribution to proceedings
    International Radiation Symposium 2012, 06.-10.08.2012, Berlin, Deutschland
    AIP Conference Proceedings, College Park, Maryland, USA: AIP Publishing, 604-607
    DOI: 10.1063/1.4804842

Publ.-Id: 19316 - Permalink


The precession dynamo experiment at HZDR
Giesecke, A.; Albrecht, T.; Gerbeth, G.; Gundrum, T.; Nore, C.; Stefani, F.; Steglich, C.;
Most planets of the solar system are accompanied by a magnetic field with a large scale structure. These fields are generated by the dynamo effect, the process that provides for the transfer of kinetic energy from a flow of a conducting fluid into magnetic energy. In case of planetary dynamos it is generally assumed that these flows are driven by thermal and/or chemical convection but other driving sources like libration, tidal forcing or precession are possible as well. Precessional forcing, in particular, has been discussed since long as an at least additional power source for the geodynamo. A fluid flow of liquid sodium, solely driven by precession, will be the source for magnetic field generation in the next generation dynamo experiment currently under development at the Helmholz-Zentrum Dresden-Rossendorf (HZDR). In contrast to previous dynamo experiments no internal blades, propellers or complex systems of guiding tubes will be used for the optimization of the flow properties. However, in order to reach sufficiently high magnetic Reynolds numbers required for the onset of dynamo action rather large dimensions of the container are necessary making the construction of the experiment a challenge. At present state a small scale water experiment is running in order to estimate the hydrodynamic flow properties in dependence of precession angle and precession rate. The measurements are utilized in combination with numerical simulations of the hydrodynamic case as input data for kinematic simulations of the induction equation. The resulting growth rates and the corresponding critical magnetic Reynolds numbers will provide a restriction of the useful parameter regime and will allow an optimization of the experimental configuration.
Keywords: Dynamo Precession
  • Poster
    AGU Fall Meeting, 09.-13.12.2013, San Francisco, USA
  • Open Access LogoContribution to proceedings
    AGU Fall Meeting, 09.-13.12.2013, San Francisco, USA

Publ.-Id: 19315 - Permalink


Velocity measurements for liquid metal batteries
Starace, M.; Weber, N.; Seilmayer, M.; Stefani, F.; Weier, T.; Galindo, V.; Eckert, S.;
Liquid metal batteries could potentially serve as a means of large-scale energy storage. The anodes of such batteries consist of liquid metals, while their cathodes consist of a liquid metal alloy. The electrodes are separated by a liquid electrolyte layer, which needs to be thin to yield a low electrical resistance and a high power output. Motion in a liquid metal battery could cause the electrodes to locally displace the electrolyte and come in contact with each other, thus shorting the battery. An electric current through a battery can subject its liquid constituents to magnetohydrodynamical instabilities. The Tayler Instability (TI) was demonstrated at the Helmholtz-Zentrum Dresden – Rossendorf. In this experiment, the magnetic field outside of a liquid GaInSn column was successfully used as an indicator of the flow [1]. The setup is now being modified to measure the vertical velocity component of the flow with ultrasonic (US) transducers in order to validate numerical simulations. As the US measurement system’s sensitivity to electrical and radio frequency noise from the current source poses an additional challenge, noise suppression mechanisms are being implemented. Furthermore, the relation between the aspect ratio of the column and the critical current, at which the TI first occurs, as well as the interfacial behavior in a two-phase system will be investigated.

Reference
[1] M. Seilmayer, F. Stefani, T. Gundrum, T. Weier, G. Gerbeth, M. Gellert, G. Rüdiger, Physical Review Letters 108, 244501 (2012).
Keywords: magnetohydrodynamics, liquid metal battery, Tayler instability
  • Poster
    549. WE-Heraeus-Seminar on Liquid Metal MHD, 15.-18.10.2013, Bad Honnef, Deutschland

Publ.-Id: 19314 - Permalink


Focusing and transport of high-intensity multi-MeV proton bunches from a compact laser-driven source
Busold, S.; Schumacher, D.; Deppert, O.; Brabetz, C.; Frydrych, S.; Kroll, F.; Joost, M.; Al-Omari, H.; Blažević, A.; Zielbauer, B.; Hofmann, I.; Bagnoud, V.; Cowan, T. E.; Roth, M.;
Laser ion acceleration provides for compact, high-intensity ion sources in the multi-MeV range. Using a pulsed high-field solenoid, for the first time high-intensity laser-accelerated proton bunches could be selected from the continuous exponential spectrum and delivered to large distances, containing more than 109 particles in a narrow energy interval around a central energy of 9.4 MeV and showing ≤30  mrad envelope divergence. The bunches of only a few nanoseconds bunch duration were characterized 2.2 m behind the laser-plasma source with respect to arrival time, energy width, and intensity as well as spatial and temporal bunch profile.

Publ.-Id: 19313 - Permalink


The THz User Facility FELBE at the Radiation Source ELBE of Helmholtz-Zentrum Dresden-Rossendorf
Seidel, W.; Drachenko, O.; Gensch, M.; Helm, M.; Kuntzsch, M.; Justus, M.; Lehnert, U.; Michel, P.; Mittendorff, M.; Schneider, C.; Schneider, H.; Schurig, R.; Teich, M.; Teichert, J.; Winnerl, S.;
The FELBE user facility located at the Helmhotz-Zentrum Dresden-Rossendorf operates two free-electron lasers (FELs). The FELs are based on the superconducting electron linear accelerator ELBE, which provides short (picosecond) electron bunches with energies up to 35 MeV at a 13 MHz repetition rate. Here we discuss the basic parameters of the FELs and the experimental opportunities at the facility.
  • Poster
    The 38th International Conference on Infrared, Millimeter and Terahertz Waves, 01.-06.09.2013, Mainz, Deutschland
  • Open Access LogoContribution to proceedings
    The 38th International Conference on Infrared, Millimeter and Terahertz Waves, 01.-06.09.2013, Mainz, Deutschland

Publ.-Id: 19312 - Permalink


Simulation of the Tayler instability in liquid metals
Weber, N.; Galindo, V.; Stefani, F.; Weier, T.;
Liquid metal batteries (LMBs), containing a stable density stratification of a heavy metal, a salt-electrolyte and a light-weight metal on the top are recently discussed as a possible means for large scale electricity storage.
Due to their completely liquid interior, LMBs are susceptible to fluid dynamic instabilities. One example is the current driven Tayler instability (TI), which will set the liquid interior in motion. Consequences of a sufficiently strong flow are electrode/electrolyte deformations, which may lead to a direct contact of the electrodes and – consequently – a battery failure.
While a simulation of the TI in astrophysical plasmas may be carried out by directly solving the induction equation, the typical very low magnetic Prandtl numbers of liquid metals makes it impossible to use this approach in our case.
For the simulation of the TI in one liquid metal electrode, we couple the Navier-Stokes-equation with a Poisson equation for the electric potential complemented by a magnetic field calculation using Biot-Savart’s law. This integro-differential formulation is implemented in the open source library OpenFOAM. Simulation matches fairly well the results obtained by a recent TI experiment. Further studies on the TI, as the influence of the batteries aspect ratio, helical flows as well as countermeasures to avoid the instability are discussed.
Keywords: Tayler instability liquid metal battery simulation OpenFOAM
  • Poster
    549. WE-Heraeus-Seminar: Liquid Metal MHD, 15.-18.10.2013, Bad Honnef, Deutschland

Publ.-Id: 19311 - Permalink


Modeling Magnetization Transfer Effects of Q2TIPS Bolus Saturation in Multi-TI Pulsed Arterial Spin Labeling
Petr, J.; Schramm, G.; Hofheinz, F.; Langner, J.; van den Hoff, J.;
Purpose: To estimate the relaxation time changes during Q2TIPS bolus saturation caused by magnetization transfer effects and to propose and evaluate an extended model for perfusion quantification which takes this into account.
Method: Three multi inversion-time pulsed arterial spin labeling sequences with different bolus saturation duration were acquired for five healthy volunteers. Magnetization transfer exchange rates in tissue and blood were obtained from control image saturation recovery. Cerebral blood flow (CBF) obtained using the extended model and the standard model was compared.
Results: A decrease of obtained CBF of 6% (10%) was observed in grey matter when the duration of bolus saturation increased from 600 to 900 ms (1200 ms). This decrease was reduced to 1.6% (2.8%) when the extended quantification model was used. Compared with the extended model, the standard model underestimated CBF in grey matter by 9.7, 15.0, and 18.7% for saturation durations 600, 900, and 1200 ms, respectively. Results for simulated single inversion-time data showed 5–16% CBF underestimation depending on blood arrival time and bolus saturation duration.
Conclusion: Magnetization transfer effects caused by bolus saturation pulses should not be ignored when performing quantification as they can cause appreciable underestimation of the CBF.

Publ.-Id: 19310 - Permalink


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 et.al., Single-Shot THz-field-driven X-ray streak camera,Nat. Photon.3(2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray 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 et.al., Single-Shot THz-field-driven X-ray streak camera,Nat. Photon.3(2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray 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 et.al., Single-Shot THz-field-driven X-ray streak camera,Nat. Photon.3(2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray 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.;
Background
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.
Results

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.
Conclusions

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

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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

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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

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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

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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.

Literatur
[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.
Literatur
[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.

References
[1] M. Butterling et al., Nucl. Instr. Meth. Phys. Res. B 269(2011) 2623.
[2] http://www.medical.siemens.com, 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


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