Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34122 Publications

How to test and verify radiation diagnostics simulations within particle-in-cell frameworks

Pausch, R.; Debus, A.; Widera, R.; Steiniger, K.; Huebl, A.; Burau, H.; Bussmann, M.; Schramm, U.

The particle-in-cell code PIConGPU provides the feature of calculating angular resolved radiation spectra in the far field based on Liénard-Wiechert potentials for all macro particles of a plasma simulation. In order to verify the physics of our code we present a series of physics test scenarios, which compare numerical results to analytic solutions of nonlinear Thomson scattering at relativistic electrons. These scenarios range from single particle and electron bunch tests to full-scale laser-plasma simulations that include the collective effects of a plasma, as well as coherent and incoherent superposition of radiation of many particles. For the calculated test cases good agreement to the theoretical results with respect to absolute spectral intensities was found in all observation directions. In an electron density scan of a laser-plasma scenario, we reproduce a second-harmonic intensity scaling also observed in experiment.

Keywords: Liénard-Wiechert potentials; Thomson scattering; laser wakefield acceleration; particle-in-cell codes; radiation; synthetic diagnostics

  • Contribution to proceedings
    1st European Advanced Accelerator Concepts, 02.-06.06.2013, La Biodola, Isola d'Elba, Italy
    Proceedings of the 1st European Advanced Accelerator Concepts, Amsterdam: Elsevier
    DOI: 10.1016/j.nima.2013.10.073
  • Nuclear Instruments and Methods in Physics Research A 740(2014), 250-256
    DOI: 10.1016/j.nima.2013.10.073

Publ.-Id: 19353

The electromagnetic sky-map radiated by the Kelvin-Helmholtz instability

Pausch, R.; Huebl, A.; Schmitt, F.; Burau, H.; Widera, R.; Pugmire, D.; Debus, A.; Juckeland, G.; Nagel, W. E.; Bussmann, M.

We present angularly resolved spectra from a Kelvin-Helmholtz instability (KHI) simulated at an unprecedented spatial, spectral and angular resolution.
This KHI simulated is a model of those KHIs expected to occur in active galactic nuclei and the afterglow of gamma-ray bursts. Our 3D, fully relativistic particle-in-cell simulation is initialized with two neighboring, counter-propagating plasma streams with initially sharp surfaces. During the simulation, a relativistic KHI extending over 9 vortices at an unprecedented resolution of 0.06 classical skin depths developed. The strong magnetic fields occurring in the KHI are a possible mechanism behind the non-thermal electromagnetic emissions from gamma-ray bursts. By simulating the far field radiation of this collisionless plasma shock using Liénard-Wiechert potentials, we obtained spectra for one quarter of the full sky map. Unique radiation signatures were linked to the particle dynamics during the formation of the relativistic, fully-3D KHI.

Keywords: Kelvin-Helmholtz instability; KHI; angularly resolved spectra; sky-map; electromagnetic radiation; Liénard-Wiechert potentials; PIConGPU

  • Poster
    Astrophysical Turbulence: From Galaxies to Planets, 07.-11.10.2013, Dresden, Deutschland

Publ.-Id: 19352

First observation of the ground-state hyperfine transition in 209Bi80+

Nörtershäuser, W.; Lochmann, M.; Jöhren, R.; Geppert, C.; Andelkovic, Z.; Anielski, D.; Botermann, B.; Bussmann, M.; Dax, A.; Frömmgen, N.; Hammen, M.; Hannen, V.; Kühl, T.; Litvinov, Y. A.; Volbrecht, J.; Stöhlker, T.; Thompson, R. C.; Weinheimer, C.; Wen, W.; Will, E.; Winters, D.; Sánchez, R. M.

The long sought after ground-state hyperfine transition in lithium-like bismuth 209Bi80+ was observed for the first time using laser spectroscopy on relativistic ions in the experimental storage ring at the GSI Helmholtz Centre in Darmstadt. Combined with the transition in the corresponding hydrogen-like ion 209Bi82+, it will allow extraction of the specific difference between the two transitions that is unaffected by the magnetic moment distribution in the nucleus and can therefore provide a better test of bound-state QED in extremely strong magnetic fields.

Keywords: ground state; transition; bismuth; lithium-like; spectroscopy; storage ring; laser; highly charged ions

Publ.-Id: 19351

Longitudinal dynamics of RF-bunched and electron-cooled ion beam at the CSRe

Wen, W. Q.; Ma, X.; Bussmann, M.; Yuan, Y. J.; Zhang, D. C.; Winters, D. F. A.; Zhu, X. L.; Li, J.; Liu, H. P.; Zhao, D. M.; Wang, Z. S.; Mao, R. S.; Zhao, T. C.; Wu, J. X.; Ma, X. M.; Yan, T. L.; Li, G. H.; Yang, X. D.; Liu, Y.; Yang, J. C.; Xia, J. W.; Xu, H. S.

Abstract: The longitudinal dynamics of RF-bunched and electron cooled ion beams have been studied at the experimental cooler storage ring (CSRe), at IMP Lanzhou. By RF-bunching the ion beam at the 50th and 100th harmonic of the revolution frequency, the longitudinal momentum spread and the bunch length of the 22Ne10+ ion beam with an energy of 70 MeV/u were measured by the new resonant Schottky pick-up and the capacitive pick-up, respectively. A minimum momentum spread of Δp/p=1.6×10−5 has been reached with less than 107 ions stored in the ring. By using the harmonic potential extracted from the Taylor expansion and the real sinusoidal potential of the bucket, the trend of momentum spread and synchrotron frequency as well as the bunch length as a function of beam current can be interpreted very well. According to this experiment, the RF-buncher is suitable for upcoming experiments on laser cooling of relativistic heavy ion beams at the CSRe.

Keywords: storage ring; ion beam; electron cooling; rf bunching; schottky

Publ.-Id: 19350

Preparations for laser cooling of relativistic heavy-ion beams at the CSRe

Wen, W.; Ma, X.; Zhang, D.; Bussmann, M.; Zhu, X.; Winters, D.; Meng, L.; Liu, H.; Zhao, D.; Wang, Z.; Li, J.; Mao, R.; Zhao, T.; Wu, J.; Li, G.; Yang, X.; Liu, Y.; Yang, J.; Yuan, Y.; Xia, J.; Xu, H.

Laser cooling is one of the most promising techniques to reach high phase-space densities for relativistic heavy-ion beams. Preparations for laser cooling of relativistic lithium-like ions, such as C 3+ and N 4+ , are being made at the experimental cooler storage ring (CSRe) in Lanzhou, China. In December 2011, a new buncher was installed and tested with a 70 MeV u-1 22 Ne 10+ ion beam by electron cooling at the CSRe. The longitudinal momentum spread of the bunched ion beam was measured by the new resonant Schottky pick-up. As a result, d” p / p ~‰ˆ 2 x— 10^-ˆ’5 has been reached at ion numbers less than 107 . According to this test result, the RF-buncher is suitable for the upcoming experiment of laser cooling at the CSRe. Laser cooling of heavy-ion beams will also be applied at future storage ring facilities, e.g. FAIR in Darmstadt, and HIAF in Lanzhou.

Keywords: rf bunching; ion beam; storage ring; schottky

Publ.-Id: 19349

A 23Na Magic Angle Spinning Nuclear Magnetic Resonance, XANES, and High Temperature X-Ray Diffraction Study of NaUO3, Na4UO5, and Na2U2O7

Smith, A. L.; Raison, P. E.; Martel, L.; Charpentier, T.; Farnan, I.; Prieur, D.; Hennig, C.; Scheinost, A. C.; Konings, R. J. M.; Cheetham, A. K.

The valence state of uranium has been confirmed for the three sodium uranates NaUVO3/[Rn](5f1), Na4UVIO5/[Rn](5f0), and Na2UVI2O7/[Rn](5f0), using X-ray absorption near-edge structure (XANES) spectroscopy. Solid-state 23Na magic angle spinning nuclear magnetic resonance (MAS NMR) measurements have been performed for the first time, yielding chemical shifts at −29.1 (NaUO3), 15.1 (Na4UO5), and −14.1 and −19 ppm (Na1 8-fold coordinated and Na2 7-fold coordinated in Na2U2O7), respectively. The [Rn]5f1 electronic structure of uranium in NaUO3 causes a paramagnetic shift in comparison to Na4UO5 and Na2U2O7, where the electronic structure is [Rn]5f0. A 23Na multi quantum magic angle spinning (MQMAS) study on Na2U2O7 has confirmed a monoclinic rather than rhombohedral structure with evidence for two distinct Na sites. DFT calculations of the NMR parameters on the nonmagnetic compounds Na4UO5 and Na2U2O7 have permitted the differentiation between the two Na sites of the Na2U2O7 structure. The linear thermal expansion coefficients of all three compounds have been determined using high-temperature X-ray diffraction: αa = 22.7 × 10–6 K–1, αb = 12.9 × 10–6 K–1, αc = 16.2 × 10–6 K–1, and αvol = 52.8 × 10–6 K–1 for NaUO3 in the range 298–1273 K; αa = 37.1 × 10–6 K–1, αc = 6.2 × 10–6 K–1, and αvol = 81.8 × 10–6 K–1 for Na4UO5 in the range 298–1073 K; αa = 6.7 × 10–6 K–1, αb = 14.4 × 10–6 K–1, αc = 26.8 × 10–6 K–1, αβ = −7.8 × 10–6 K–1, and αvol = −217.6 × 10–6 K–1 for Na2U2O7 in the range 298–573 K. The α to β phase transition reported for the last compound above about 600 K was not observed in the present studies, either by high-temperature X-ray diffraction or by differential scanning calorimetry.

Keywords: XANES; NMR; XRD; uranates

Publ.-Id: 19348

Cetuximab Attenuates Its Cytotoxic and Radiosensitizing Potential by Inducing Fibronectin Biosynthesis

Eke, I.; Storch, K.; Krause, M.; Cordes, N.

Inherent and acquired resistance to targeted therapeutics continues to emerge as a major clinical obstacle. For example, resistance to EGF receptor targeting occurs commonly, more so than was expected, on the basis of preclinical work. Given emerging evidence that cancer cell-substrate interactions are important determinants of therapeutic sensitivity, we examined the impact of cell-fibronectin interactions on the efficacy of the EGF receptor antibody cetuximab, which is used widely for lung cancer treatment. Our results revealed the potential for cell-fibronectin interactions to induce radioresistance of human non-small cell lung cancer cells. Cell adhesion to fibronectin enhanced tumor cell radioresistance and attenuated the cytotoxic and radiosensitizing effects of cetuximab. Both in vitro and in vivo, we found that cetuximab treatment led to a remarkable induction of fibronectin biosynthesis. Mechanistic analyses revealed the induction was mediated by a p38-MAPK-ATF2 signaling pathway and that RNAi-mediated inhibition of fibronectin could elevate the cytotoxic and radiosensitizing potential of cetuximab. Taken together, our findings show how cell adhesion blunts cetuximab, which, by inducing fibronectin, generates a self-attenuating mechanism of drug resistance.


Publ.-Id: 19347

Influence and Compensation of Truncation Artifacts in MR-Based Attenuation Correction in PET/MR

Schramm, G.; Langner, J.; Hofheinz, F.; Petr, J.; Lougovski, A.; Beuthien-Baumann, B.; Platzek, I.; van den Hoff, J.

The goal of this article is to quantify the influence of truncation artifacts in the magnetic resonance (MR)-based attenuation map (MRMap) on reconstructed positron emission tomography (PET) image volumes and to propose a new method for minimizing this influence. Methods: PET data sets of 20 patients investigated in a Philips Ingenuity PET/MR were reconstructed with and without applying two different methods for truncation compensation (TC1 vendor-provided, TC2 newly developed). In this patient group, the extent of truncation artifacts and quality of the truncation compensation (TC) was assessed visually in the MRMaps. In three additional patients MRMaps generated by algorithm TC2 could be compared to the ground truth of transmission-based attenuation maps obtained with a Siemens ECAT {rm HR}^{+} scanner. The influence of truncation on regional SUVs in lesions, other hot structures (bladder, kidney, myocardium) and the arms was assessed in suitable volume of interests (VOI). Results: Truncation compensated MRMaps exhibited residual artifacts in the arms in 16 patients for algorithm TC1 and to a lesser extent in eight patients for algorithm TC2. Compared to the transmission-based attenuation maps algorithm TC2 slightly overestimated the size of the truncated arms by 0.3 cm in the radial direction. Without truncation compensation, VOIs located in the trunk showed an average {rm SUV}_{max} underestimation of less than 5.4% relative to the results obtained with TC2. Inside the patients' arms underestimations up to 46.5% were found. Conclusion: In the trunk, standardized uptake values (SUV) underestimations due to truncation artifacts in the MRMap are rather small. Inside the arms, severe SUV underestimations can occur. Therefore, reliable TC is mandatory and can be achieved by applying the newly developed algorithm TC2 which has y- elded promising results so far. Implementation of the proposed method is straightforward and should be easily adaptable to other PET/MR systems.

Publ.-Id: 19346

Atomic layer deposition of TiO2 from tetrakis(dimethylamino) titanium and H2O

Abendroth, B.; Moebus, T.; Rentrop, S.; Strohmeyer, R.; Vinnichenko, M.; Weling, T.; Stocker, H.; Meyer, D. C.

The atomic layer deposition (ALD) of TiO2 from tetrakis(dimethylamino) titanium(TDMAT) and water was studied in the substrate temperature (T-S) range of 120 degrees C to 330 degrees C.
The effect of deposition temperatures on the resulting layer microstructure is investigated. Based on the experimental results, possible interaction mechanisms of TDMAT and H2O precursor molecules and the TiO2 surface at different temperatures are discussed. The TiO2 layers were characterized with respect to microstructure, composition and optical properties by glancing angle x-ray diffraction and reflectometry, x-ray fluorescence analysis, photoelectron spectroscopy and spectroscopic ellipsometry. A constant layer growth with increasing number of ALD cycles was achieved for all investigated deposition temperatures, if the inert gas purge time after the H2O pulse was increased from 5 s at temperatures below 250 degrees C to 25 s for T-S >= 320 degrees C. In the investigated temperature range, the growth per cycle varies between 0.33 and 0.67 angstrom/cycle with a minimum at 250 degrees C. The variations of the deposition rate are related to a change from a surface determined decomposition of TDMAT to a gas phase decomposition route above 250 degrees C. At the same temperature, the microstructure of the TiO2 layers changes from amorphous to predominately crystalline, where both anatase and rutile are present.

Publ.-Id: 19345

An automatic method for accurate volume delineation of heterogeneous tumors in PET

Hofheinz, F.; Langner, J.; Petr, J.; Beuthien-Baumann, B.; Steinbach, J.; Kotzerke, J.; van den Hoff, J.

Purpose: Accurate volumetric tumor delineation is of increasing importance in radiation treatment planning. Many tumors exhibit only moderate tracer uptake heterogeneity and delineation methods using an adaptive threshold lead to robust results. These methods use a tumor reference value R (e. g., ROI maximum) and the tumor background Bg to compute the volume reproducing threshold. This threshold corresponds to an isocontour which defines the tumor boundary. However, the boundaries of strongly heterogeneous tumors can not be described by an isocontour anymore and therefore conventional threshold methods are not suitable for accurate delineation. The aim of this work is the development and validation of a delineation method for heterogeneous tumors.

Methods: The new method (voxel-specific threshold method, VTM) can be considered as an extension of an adaptive threshold method (lesion-specific threshold method, LTM), where instead of a lesion-specific threshold for the whole ROI, a voxel-specific threshold is computed by determining for each voxel Bg and R in the close vicinity of the voxel. The absolute threshold for the considered voxel is then given by T-abs = T x (R - Bg) + Bg, where T = 0.39 was determined with phantom measurements. Validation: 30 clinical datasets from patients with non-small-cell lung cancer were used to generate 30 realistic anthropomorphic software phantoms of tumors with different heterogeneities and well-known volumes and boundaries. Volume delineation was performed with VTM and LTM and compared with the known lesion volumes and boundaries.

Results: In contrast to LTM, VTM was able to reproduce the true tumor boundaries accurately, independent of the heterogeneity. The deviation of the determined volume from the true volume was (0.8 +/- 4.2)% for VTM and (11.0 +/- 16.4)% for LTM.

Conclusions: In anthropomorphic software phantoms, the new method leads to promising results and to a clear improvement of volume delineation in comparison to conventional background-corrected thresholding. In the next step, the suitability for clinical routine will be further investigated. (C) 2013 American Association of Physicists in Medicine.

Keywords: PET; ROI delineation; heterogeneous tumors

Publ.-Id: 19344

GaPN dilute nitride fabricated by ion-implantation and pulsed laser melting

Gao, K.; Prucnal, S.; Baehtz, C.; Skorupa, W.; Helm, M.; Zhou, S.

It is challenging to achieve luminescence from GaP due to its indirect bandgap. This restricts the application of GaP for photonic devices.
In this contribution we present the broad-band luminescence from a multi-energy-level structure based on GaP. Such optically active layer is performed by nitrogen-implantation into commercial (100) GaP wafers followed by nanosecond-range pulsed laser melting. The microstructural and optical properties of the fabricated GaPN/GaP samples were investigated by means of X-ray diffraction (XRD), micro-Raman spectroscopy, photoluminescence (PL) and photoreflectance (PR) spectroscopy. The XRD results indicate that the pulsed laser treatment leads to the recrystallization of the implantation-induced amorphous layer and the incorporation of nitrogen into the GaP lattice. The PL spectra confirm directly the formation of optically active diluted nitride layer. Moreover, the obtained multi-band PL and micro-Raman spectra suggest a local enrichment of nitrogen in the implanted layer, i.e., the formation of GaN/GaN1-xPx crystallites, which are embedded in a porous GaP1-yNy/GaP layer. Such system exhibits a wide range of strong luminescence and absorption from 380 nm to 700 nm. The structure has promising prospects in photovoltaic and white-light-emitting applications.

Keywords: GaPN; ion-implantation; pulsed laser melting

  • Lecture (Conference)
    E-MRS 2013 Fall Meeting, 16.-20.09.2013, Warsaw, Poland

Publ.-Id: 19342

Radionuclide impurities in [F-18]F- and [F-18]FDG for positron emission tomography

Koehler, M.; Degering, D.; Zessin, J.; Fuechtner, F.; Konheiser, J.

The paper describes radionuclide impurities (gamma-emitters and H-3) in proton irradiated O-18 enriched water from an Nb target vessel with Nb entrance window, their distribution in different synthesis steps and finally in the PET radiopharmaceuticals [F-18]Fluoride and [F-18]FDG.

Keywords: 18F; PET; radionuclidic purity

Publ.-Id: 19341

Insitu STXM imaging and resistance measurements of trilayer vortices

Banholzer, A.; Wintz, S.; Fowley, C.; Deac, A.; Raabe, J.; Lenz, K.; Lindner, J.; Fassbender, J.

We investigate a trilayer vortex system by simultaneous scanning trans-mission X-ray microscopy (STXM) and in-situ giant magnetoresistance (GMR) measurements. Our aim is to correlate the magnetic conguration of both magnetic layers with the corresponding magneto-resistance effects.
The sample is a Co/Cu/NiFe cylindrical trilayer, with 2 micrometer diameter. Top and bottom contacts allow to apply a perpendicular DC current to measure the resistance. Simultaneously the magnetic conguration of each element of the disc is imaged using STXM. This is performed at the Paul Scherrer Institute. The vortex core formation in both magnetic layers and the position of the vortex core can be controlled by applying an in-plane external magnetic eld. When the cores are at the edge, and the magnetization state resembles that of two in-plane magnetized disks, the GMR is low, as both cores move towards the center. With decreasing field the resistance increases, as the cores move beyond the center and towards the opposite side, the resistance decreases again. We investigate the resistance at different DC currents in dependency on the swept magnetic fields.

Keywords: vortex; STXM; GMR

  • Poster
    17. Deutsche Physikerinnentagung, 31.10.-03.11.2013, Heidelberg, Deutschland

Publ.-Id: 19340

Automated evaluation of setup errors in carbon ion therapy using PET: feasibility study

Kuess, P.; Helmbrecht, S.; Fiedler, F.; Birkfellner, W.; Enghardt, W.; Hopfgartner, J.; Georg, D.

Purpose: To investigate the possibility of detecting patient mispositioning in carbon-ion therapy with particle therapy PET in an automated image registration based manner.
Methods: Tumors in the head and neck (H&N), pelvic, lung and brain region were investigated. Biologically optimized carbon ion treatment plans were created with TRiP98. From this treatment plans the reference +-activity distributions were calculated using a Monte Carlo simulation. Setup errors were simulated by shifting or rotating the CT. The expected + activity was calculated for each plan with shifts. Finally, the reference particle therapy PET images were compared to the "shifted" +-activity distribution simulations using the Pearson's correlation coecient (PCC). To account for dierent PET monitoring options the in-beam PET was compared to three dierent in-room scenarios. Additionally the dosimetric eects of the CT misalignments were investigated.
Results: The automated PCC detection of patient mispositioning was possible in the investigated indications for cranio-caudal shifts of 4 mm and more, except for prostate tumors. In the rather homogeneous pelvic region the generated +-activity distribution of the reference and compared PET image were to much alike. Thus setup errors in this region could not be detected. Regarding lung lesions the detection strongly depended on the exact tumor location: in the center of the lung tumor misalignments could be detected down to 2 mm shifts while resolving shifts of tumors close to the thoracic wall was more challenging. Rotational shifts in the H&N and lung region of +6 and more could be detected using in-room PET and partly using in-beam PET. Comparing in-room PET to in-beam PET no obvious trend was found. However, among the in-room scenarios a longer measurement time was found to be advantageous.
Conclusion: This study scopes the use of various particle therapy PET verication techniques in four indications. The automated detection of patients' setup errors was investigated in a broad accumulation of data sets. The evaluation of introduced setup errors is performed automatically, which is of utmost importance to introduce highly required particle therapy monitoring devices into the clinical routine.

Keywords: in-beam PET; PT-PET; Pearson's correlation coefficient; in-vivo Dosimetry; TRiP98

Publ.-Id: 19339

Charakterisierung der Wechselwirkung von Selen mit dem Bakterium Azospirillum brasilense

Maffert, A.

In der vorliegenden Arbeit konnte gezeigt werden, dass das Wachstum von Azospirillum brasilense durch die Selenoxianionen Selenat und Selenit unterschiedlich beeinflusst wird. Selenat hatte im Rahmen der untersuchten Bedingungen kein Einfluss auf das Bakterium und wurde auch nicht reduziert. Dahingegen konnte beobachtet werden, dass das Bakterium sensitiv gegenüber Selenit ist. Im über die optische Dichte der Zellkultur und die Gesamtzellproteinkonzentration dokumentierten Wachstumsverlauf wurde ersichtlich, dass die Kultur in Gegenwart von Selenit erst nach vergleichsweise langer lag-Phase wächst und auch mit der Reduktion des Selenits zu elementarem Selen beginnt. Die sphärische nanopartikuläre Form des mikrobiell gebildeten elementaren Selens konnte über verschieden mikroskopische Techniken dargestellt werden. Im Folgenden ist es gelungen die Nanopartikel durch Adaption einer aus der Literatur bekannten Methode von den Bakterienzellen zu separieren. Über Elektronenmikrokopie gekoppelt mit Elementanalysen sowie die Ramanspektroskopie konnte die Zusammensetzung und Struktur der Nanopartikel als Selen- und Schwefel-haltig analysiert werden. Zudem konnte über dynamische Lichtstreuung und Zetapotentialmessungen Aussagen über die mittlere Größe der Partikel von 400 nm und das negative Oberflächenpotential getroffen werden.

Keywords: selenium; micobial reduction; selenite

  • Master thesis
    Internationales Hochschulinstitut Zittau, 2013
    77 Seiten

Publ.-Id: 19338

Magnetic-polaron–induced colossal magnetocapacitance in CdCr2S4

Xie, Y. M.; Yang, Z. R.; Zhang, Z. T.; Yin, L. H.; Chen, X. L.; Song, W. H.; Sun, Y. P.; Zhou, S.; Tong, W.; Zhang, Y. H.

The origin of colossal magnetoresistance and colossal magnetocapacitance in a CdCr2S4 system was investigated. Thermoelectric-power and electronic spin resonance spectra reveal that the magnetic polaron is responsible for the colossal magnetoresistance in the n-type sample. The existence of magnetic polarons in the paramagnetic insulting matrix forms an intrinsic Maxwell-Wagner system, leading to the appearance of colossal magnetocapacitance. Being consistent with the evolution of magnetic polarons upon cooling, the Maxwell-Wagner system is valid around insulator-metal transition, where the resistance derived from impedance spectroscopy matches perfectly with DC resistance.

Publ.-Id: 19337

Establishment of two complementary in vitro assays for radiocopper complexes

Kubeil, M.; Zarschler, K.; Stephan, H.

kein Abstract verfügbar

  • Lecture (Conference)
    2nd Annual Meeting Helmholtz Virtual Institute, 06.-08.10.2013, Heidelberg, Deutschland

Publ.-Id: 19336

64Cu-Markierung eines Cyclampropionsäure-Peptid-Konjugats zum EGFR-Targeting

Kubeil, M.; Viehweger, K.; Steinbach, J.; Stephan, H.

Für die Entwicklung von 64Cu-basierten-Radiopharmaka erweisen sich makrocyclische Tetraamin-Chelatoren als überaus interessant. Sie bieten die Möglichkeit, Kupferradionuklide stabil zu binden und erlauben die Einführung von zielsuchenden Einheiten (Peptide, Proteine, Antikörper) an das Grundgerüst, um ein pharmazeutisches Targeting zu erzielen. Es ist bekannt, dass Cyclam-Monopropionsäure (TE1P) stabile Kupfer(II)-Komplexe bildet [1]. Komplexe mit Radiokupfer sind bisher nicht beschrieben worden. Dieses Chelatorsystem eignet sich für eine Mehrfachfunktionalisierung mit zielsuchenden Einheiten und damit ergibt sich die Möglichkeit, multivalente Wechselwirkungen mit Rezeptoren auszunutzen. Das kann zum einen zu einer höheren Bindungsaffinität und zum anderen zu einer Erhöhung der metabolischen Stabilität führen. Exemplarisch wird als rezeptorbindende Einheit das Dodecapeptid GE11 (YHWYGYTPQNVI) verwendet, welches spezifisch am epidermalen Wachstumsfaktor Rezeptor (Epidermal-Growth-Factor-Receptor, EGFR) bindet [2].
Es werden die Synthese zur Mehrfachfunktionalisierung der Cyclam-Monopropionsäure (TE1P) mit einem EGFR-spezischen Peptid (GE11) vorgestellt sowie radiochemische Aspekte bezüglich der Markierung mit 64Cu diskutiert. Darüber hinaus werden Aussagen zur metabolischen Stabilität und zur Bindungsaffinität gegenüber dem EGFR getroffen, um das Potenzial dieses 64Cu-markierten Konjugats für eine radiopharmazeutische Anwendung zu bewerten.

[1] T. A. Kaden et al., Helv. Chim. Acta, 1986, 69, 2081. [2] Z. Li et al., Faseb J. 2005,
19, 1978.

  • Poster
    GDCh-Wissenschaftsforum Chemie 2013, 01.-04.09.2013, Darmstadt, Deutschland

Publ.-Id: 19335

High-yield production of functional soluble single-domain antibodies in the cytoplasm of Escherichia coli

Zarschler, K.; Witecy, S.; Kapplusch, F.; Foerster, C.; Stephan, H.

For their application in the area of diagnosis and therapy, single-domain antibodies (sdAbs) offer multiple advantages over conventional antibodies and fragments thereof in terms of size, stability, solubility, immunogenicity, production costs as well as tumor uptake and blood clearance. Thus, sdAbs have been identified as valuable next-generation targeting moieties for molecular imaging and drug delivery in the past years. Since these probes are much less complex than conventional antibody fragments, bacterial expression represent a facile method in order to produce sdAbs in large amounts as soluble and functional proteins.

By the combined use of high cell density cultivation media with a genetically engineered E. coli mutant strain designed for the cytoplasmic formation of proper disulfide bonds, we achieved high level of intracellular sdAb production (up to 200 mg/L). Due to a carboxyterminal hexahistidine epitope, the soluble recombinant sdAbs could be purified by one-step immobilized metal affinity chromatography to apparent homogeneity and easily radiolabeled with 99mTc within 1 h. The intradomain disulfide bridge being critical for the stability and functionality of the sdAb molecule was shown to be properly formed in ~96% of the purified proteins. In vitro binding studies confirmed the high affinity and specificity of the expressed sdAb 7C12 towards its molecular target.

Our study demonstrates an efficient cultivation and expression strategy for the production of substantial amounts of soluble and functional sdAbs, which may be adopted for high-yield production of other more complex proteins with multiple disulfides as well.

Publ.-Id: 19334

Damage accumulation in pure iron and high concentrated Fe–12.5 at% Cr alloy: comparison between object kinetic Monte Carlo and cluster dynamics

Gokhman, A.; Caturla, M.; Bergner, F.

A comparison between object kinetic Monte Carlo (OKMC) and cluster dynamics (CD) simulations of damage accumulation has been made in the domain of low (77–150 K) temperatures for electronirradiated and then annealed pure iron as well as at 573K temperature for neutron-irradiated high concentrated Fe–12.5 at% Cr alloy. Findings indicate that an increase in the size of the simulation box up to 300 nm × 300 nm × 300 nm in OKMC simulation and direct integration of master equation of CD provide the quantitative agreement results of these methods among themselves as well as with the experimental data of microstructure evolution of Fe–12.5 at% Cr alloy and qualitative agreement for the case of pure iron electron irradiated at 77K and then annealed at temperatures between 77 and 150 K.

Keywords: irradiation; pure iron; Fe–Cr alloy; cluster dynamics; object kinetic Monte Carlo

Publ.-Id: 19333

Critical assessment of Cr-rich precipitates in neutron-irradiated Fe–12 at%Cr: Comparison of SANS and APT

Bergner, F.; Pareige, C.; Kuksenko, V.; Malerba, L.; Pareige, P.; Ulbricht, A.; Wagner, A.

Neutron irradiation at 300 °C up to 0.6 dpa of an industrial purity Fe–12at%Cr alloy gives rise to the formation of Cr-rich precipitates of radii of about 1 nm. Small-angle neutron scattering (SANS) and atom probe tomography (APT) applied to the same material should reveal consistent characteristics of the irradiation-induced features. They roughly do so with respect to size and volume fraction, but they do not with respect to the composition of the precipitates or clusters. The discrepancy was expressed in terms of the Porod invariant of nuclear SANS. This quantity can be determined directly by integrating the measured nuclear difference scattering cross section or, alternatively, estimated from the APT results. Both
estimates were compared taking into account all potential sources of deviation including error propagation. We have found that the deviation is significant and can be progressively removed by artificially reducing the Fe fraction in the Cr-rich clusters with respect to the measured value. A well-known effect of this kind is the different evaporation fields of Cr-rich clusters and the Fe-rich matrix and resulting ion trajectory overlaps in APT. State-of-the-art consideration of this effect indicates, however, that it is not sufficient to remove the observed discrepancy.

Keywords: Small-angle neutron scattering; Atom probe tomography; Fe-Cr alloys. Irradiation effects

Publ.-Id: 19332

PIConGPU - Ultrafast OpenSource Plasma Physics

Bussmann, M.; Burau, H.; Cowan, T. E.; Debus, A.; Helm, A.; Huebl, A.; Juckeland, G.; Kluge, T.; Nagel, W. E.; Pausch, R.; Schmitt, F.; Schneider, B.; Schramm, U.; Steiniger, K.; Widera, R.

PIConGPU is a fully relativistic 3D3V particle-in-cell (PIC) code for studing laser-plasma physics. Todays GPUs can be used as hardware accelerators, approaching a new era of fast in situ plasma simulations.

PIC codes became the working-horses for theoretical studies of laser-plasma interactions. PIConGPU has been developed for ion and electron acceleration experiments as well as for studing plasma instabilities. It is accompanied by a still-growing set of live-analysis plugins, e.g. far-field radiation diagnostics and live 3D imaging.

With its outstanding performance up to 8 PFlops/s on the TOP2 supercomputer Titan (Oak Ridge National Lab), PIConGPU is one of the Gordon-Bell-Prize finalists 2013. It has been shown that it runs efficiently on up to 18,000 GPUs, utilizing a total of 50 million multi-processors.

Its OpenSource development is carried out by the Junior Group Computational Radiation Physics at the Institute for Radiation Physics at HZDR in close collaboration with the Center for Information Services and High Performance Computing (ZIH) of the Technical University Dresden (TUD).

  • Invited lecture (Conferences)
    Plasma Seminar October 2013, 23.10.2013, Rehovot, Israel

Publ.-Id: 19331

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

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 Logo Physics Procedia 47(2013), 178-183
    DOI: 10.1016/j.phpro.2013.06.026

Publ.-Id: 19329

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

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

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


Publ.-Id: 19326

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

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

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

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

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

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

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 Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A43


Publ.-Id: 19319

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.


[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

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

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 Logo Contribution 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

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 Logo Contribution to proceedings
    AGU Fall Meeting, 09.-13.12.2013, San Francisco, USA

Publ.-Id: 19315

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.

[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

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

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 Logo Contribution to proceedings
    The 38th International Conference on Infrared, Millimeter and Terahertz Waves, 01.-06.09.2013, Mainz, Deutschland

Publ.-Id: 19312

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

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

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 Logo Contribution 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Super-radiant THz sources: Challenges and opportunities

Gensch, M.

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

[1]G.L. Carr et. al., High power terahertz radiation from relativistic electrons,Nature420(2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol.51(2008), 423.
[3]U. Fruehling, Single-Shot THz-field-driven X-ray streak camera,Nat. Photon.3(2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray Lightsources,Nat. Photon.5(2011), 162.
[5]D. Daranciang et. al.,Single cycle terahertz pulses with > 0.2 V/angstrom field amplitudes via coherent transition radiation, Appl. Phys.
Lett.(2011), 141117.

Keywords: THz control of matter; ultra-fast phenomena; high field driven processes

  • Invited lecture (Conferences)
    Seminar of the Department of Physics and Photon Science at the Gwangju Institute of Science and Technology (GIST), 27.09.2013, Gwangju, South Korea

Publ.-Id: 19293

Super-radiant THz sources: Challenges and opportunities

Gensch, M.

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

[1]G.L. Carr et. al., High power terahertz radiation from relativistic electrons,Nature420(2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol.51(2008), 423.
[3]U. Fruehling, Single-Shot THz-field-driven X-ray streak camera,Nat. Photon.3(2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray Lightsources,Nat. Photon.5(2011), 162.
[5]D. Daranciang et. al.,Single cycle terahertz pulses with > 0.2 V/angstrom field amplitudes via coherent transition radiation, Appl. Phys.
Lett.(2011), 141117.

Keywords: super-radiant THz; ultra-fast phenomena

  • Invited lecture (Conferences)
    Seminar of the Center for Quantum-beam-based Radiation Research, KAERI, 25.09.2013, Daejeon, South Korea

Publ.-Id: 19292

Super-radiant THz sources: Challenges and opportunities

Gensch, M.

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

[1]G.L. Carr et. al., High power terahertz radiation from relativistic electrons,Nature420(2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol.51(2008), 423.
[3]U. Fruehling, Single-Shot THz-field-driven X-ray streak camera,Nat. Photon.3(2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray Lightsources,Nat. Photon.5(2011), 162.
[5]D. Daranciang et. al.,Single cycle terahertz pulses with > 0.2 V/angstrom field amplitudes via coherent transition radiation, Appl. Phys.
Lett.(2011), 141117.

Keywords: super-radiant THz; ultra-fast phenomena

  • Invited lecture (Conferences)
    Seminar of the Pohang Accelerator Laboratory (PAL), 24.09.2013, Pohang, South Korea

Publ.-Id: 19291

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

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

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

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

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

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

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

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

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

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

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

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 Logo Contribution 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

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

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

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

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

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

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

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

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

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

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

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

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

Radiofluorination and biological evaluation of N-aryl-oxadiazolyl-propionamides as potential radioligands for PET imaging of cannabinoid CB2 receptors

Teodoro, R.; Moldovan, R.-P.; Lueg, C.; Günther, R.; Donat, C. K.; Ludwig, F.-A.; Fischer, S.; Deuther-Conrad, W.; Wünsch, B.; Brust, P.

The level of expression of cannabinoid receptor type 2 (CB2R) in healthy and diseased brain has not been fully elucidated. Therefore, there is a growing interest to assess the regional expression of CB2R in the brain. Positron emission tomography (PET) is an imaging technique, which allows quantitative monitoring of very low amounts of radiolabelled compounds in living organisms at high temporal and spatial resolution and, thus, has been widely used as a diagnostic tool in nuclear medicine. Here, we report on the radiofluorination of N-aryl-oxadiazolyl-propionamides at two different positions in the lead structure and on the biological evaluation of the potential of the two tracers [18F]1 and [18F]2 as CB2 receptor PET imaging agents.

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

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

Keywords: Blood–brain barrier; Cannabinoid receptors; 18F labelling; Molecular imaging; Positron emission tomography

Publ.-Id: 19265

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

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

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

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

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

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

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

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 Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-039 2013
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 19256

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 Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-038 2013
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 19255

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

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 Logo Contribution to proceedings
    FEL2013 - 35th international Free-Electron Laser Conference, 26.-30.08.2013, New York, USA

Publ.-Id: 19253

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 Logo Contribution to proceedings
    SRF 2013 - 16th International conference on RF Superconductivity, 23.-27.09.2013, Paris, France
    Proceedings of SRF 2013
  • Poster
    SRF 2013 - 16th International conference on RF Superconductivity, 23.-27.09.2013, Paris, France


Publ.-Id: 19252

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 Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-004 2011
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 19251

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

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