Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32227 Publications
The importance of hole concentration in establishing carrier-mediated ferromagnetism in Mn doped Ge
Zhou, S.; Bürger, D.; Skorupa, W.; Oesterlin, P.; Helm, M.; Schmidt, H.;
In the present work, we have prepared Mn-doped Ge using different annealing approaches after Mn ion implantation, and obtained samples with hole concentrations ranging from 1018 to 2.1$\times$1020 cm-3, the latter being the highest reported so far. Based on the magneto-transport properties of Mn doped Ge, we argue that the hole concentration is a decisive parameter in establishing carrier-mediated ferromagnetism in magnetic Ge.
Keywords: Diluted magnetic semiconductor, Ge, ion implantation

Publ.-Id: 14023 - Permalink


Hysteresis in the magnetotransport of manganese-doped germanium: Evidence for carrier-mediated ferromagnetism
Zhou, S.; Bürger, D.; Mücklich, A.; Baumgart, C.; Skorupa, W.; Timm, C.; Oesterlin, P.; Helm, M.; Schmidt, H.;
We report the fabrication of Ge:Mn ferromagnetic semiconductors by Mn-ion implantation into Ge followed by pulsed laser annealing. Benefiting from the short time annealing, the hole concentration in Mn-implanted Ge has been increased by two orders of magnitude from 1018 to over 1020 cm−3. Likely due to the high hole concentration, we observe that the longitudinal and Hall resistances exhibit the same hysteresis as the magnetization, which is usually considered as a sign of carrier-mediated ferromagnetism.
Keywords: Diluted magnetic semiconductor, Ge, Ion implantation

Publ.-Id: 14022 - Permalink


New high-spin isomer and quasiparticle-vibration coupling in 187Ir
Modamio, V.; Jungclaus, A.; Algora, A.; Bazzacco, D.; Escrig, D.; Fraile, L. M.; Lenzi, S.; Marginean, N.; Martinez, T.; Napoli, D. R.; Schwengner, R.; Ur, C. A.;
The nucleus 187 Ir has been populated up to high spin using the reaction 186 W(7 Li, 6n) at a beam energy of 59 MeV. A comprehensive extension of its level scheme has been proposed comprising 116 newly established excited states connected by 194 transitions which have been observed for the first time. All known rotational bands have been extended up to higher spin and in particular the band crossing region of the h9/2 band has been revised. A number of new intrinsic high-K states has been identified and for some of them multi-quasiparticle configurations have been tentatively assigned. The three-quasiparticle state with spin 29/2- and an excitation energy of 2487 keV is isomeric with a half-live of T1/2 = 1.8(5) µs. On top of this state a rich level scheme reaching up to spin (59/2-) and excitation energies around 7 MeV has been established. Of particular interest is a new structure built on the 31/2-, maximum spin three-quasiparticle state with {11/2-[505]} {11/2+[615],9/2+[624]} configuration at 2755 keV. Arguments have been presented which indicate a vibrational character of these states similar to the proposed vibration-plus-quasiparticle coupling suggested for the structure built on the 11/2- h11/2 proton 1qp state.
Keywords: nuclear structure, gamma-ray spectroscopy, high-spin isomer, vibration-particle coupling

Publ.-Id: 14021 - Permalink


Anwendung zeitmodulierter AC-Magnetfelder zur Strömungskontrolle in metallischen Schmelzen
Räbiger, D.; Eckert, S.; Gerbeth, G.;
In dieser Arbeit wird die Wirkung des elektromagnetischen Rührens der Restschmelze bei der gerichteten Erstarrung einer Al-Si-Legierung untersucht. Dabei werden neue Methoden zum elektromagnetischen Rühren unter Nutzung eines zeitlich modulierten rotierenden Magnetfeldes (RMF) und eines wandernden Magnetfeldes (TMF) vorgestellt. Beim elektromagnetischen Rühren mit kontinuierlich wirkenden Feldern treten oft strömungsinduzierte Entmischungen im Gefüge auf. Mit der Strategie der Nutzung zeitmodulierter Felder sollen diese bekannten Nachteile vermieden werden. Die Ergebnisse zeigen, dass das Rühren unter Anwendung eines modulierten magnetischen Feldes Möglichkeiten zur effizienten Kontrolle des Strömungsfeldes vor der Erstarrungsfront bietet.
Keywords: Flow control, Electromagnetic stirring, liquid metal
  • Lecture (Conference)
    Symposion zur Simulation metallurgischer Strömungsprozesse an österreichischen und deutschen Universitäten, 16.-19.06.2010, Kirnitzschtal, Deutschland

Publ.-Id: 14020 - Permalink


Anwendung zeitmodulierter AC-Magnetfelder zum Rühren metallischer Schmelzen während der Erstarrung einer Al-Si-Legierung
Räbiger, D.; Leonhardt, M.; Eckert, S.; Gerbeth, G.;
Der Einsatz elektromagnetischer Felder zum Rühren metallischer Schmelzen stellt eine elegante Möglichkeit einer völlig kontaktlosen Strömungskontrolle in erstarrenden Metalllegierungen dar, wobei die Strömungsintensität über die elektrischen Regelgrößen Strom und Frequenz gesteuert werden kann.
Trotz der nachweislichen Verbesserung der Gefügeeigenschaften, wie Kornfeinung und Vergrößerung des equiaxialen Erstarrungsbereiches durch eine intensive Strömung im Bereich der Erstarrungsfront, ist der Einsatz des elektromagnetischen Rührens auch problembehaftet, da die Strömung negative Auswirkungen wie strömungsinduzierte Porosität oder Gefügeinhomogenitäten (z.B. weiße Bänder beim Stahlguss) hervorrufen kann. Diese Nachteile erschweren eine industrielle Anwendung des Verfahrens im Strangguss.
Der Einsatz maßgeschneiderter, zeitmodulierter Magnetfelder bietet die Perspektive, die oben genannten, nachteiligen Effekte zu vermeiden. Mit dem Konzept der maßgeschneiderten Magnetfelder werden geeignete Strömungen erzeugt, welche die für die Herausbildung vorteilhafter Gefüge notwendigen Temperatur- und Konzentrationsfelder in der erstarrenden Schmelze liefern. Dies erfordert jedoch ein genaues Verständnis der Wechselwirkung von Magnetfeld, induzierter Strömung und Erstarrungsvorgang.
In diesem Vortrag wird die Wirkung des elektromagnetischen Rührens der Restschmelze mittels zeitmodulierter Magnetfelder bei der gerichteten Erstarrung einer binären Al-Si-Legierung untersucht. Für eine erfolgreiche Anwendung dieses Verfahrens sind geeignete Kombinationen der Magnetfeldparameter zu ermitteln. Zu diesem Zweck wurden Strömungsmessungen in einer isothermen Modellschmelze unter dem Einfluss modulierter Magnetfelder durchgeführt. Aufbauend auf den gewonnenen Erkenntnissen zur zeitlichen Entwicklung der Strömungsstruktur wurden geeignete Strategien für eine gezielte Beeinflussung der Gefügemerkmale durch den Einsatz maßgeschneiderter Magnetfelder abgeleitet. Die Erstarrungsversuche demonstrieren, dass es möglich ist, mit Hilfe zeitmodulierter magnetischer Felder korngefeinte, equiaxiale Gefüge unter Vermeidung der Herausbildung makroskopischer Gefügeinhomogenitäten herzustellen.
Die Ergebnisse veranschaulichen das große Potenzial des elektromagnetischen Rührens zur Verbesserung der Materialeigenschaften der erstarrten Struktur und einer Optimierung der Prozesskontrolle.
Keywords: Al-Si alloy, Electromagnetic stirring, Rotating magnetic field, Solidification, Columnar to equiaxed transition (CET), Grain refinement
  • Lecture (Conference)
    Tagung Stranggiessen, 15.-17.11.2010, Neu-Ulm, Deutschland
  • Contribution to proceedings
    Tagung Stranggiessen, 15.-17.11.2010, Neu-Ulm, Deutschland
    Stranggießen, Frankfurt: Werkstoff-Informationsgesellschaft mbH, 978-3-88355-384-9, 163-168

Publ.-Id: 14019 - Permalink


Terahertz free-electron lasers and their applications for the spectroscopy of solids
Helm, M.;
In free-electron lasers (FEL) optical gain and stimulated emission are provided by relativistic electrons, wiggling through a periodic magnetic-field arrangement. Since the emitted wavelength only depends on the energy of the electrons and the magnetic field strength, an in principle arbitrary lasing wavelength may be achieved. Thus FELs are mostly used in spectral ranges, where conventional lasers with reasonably high power hardly exist. This is true, among others, for the long-wavelength infrared and terahertz (THz) range and represents the motivation to build such bulky THz sources.

Here I will discuss the operation principle of an FEL and then describe the THz FEL at FZD in Dresden. This FEL, called FELBE, was first operated in 2004 and covers now a wavelength range of nearly two spectral decades (3-300 µm or 1-100 THz). The key feature which distinguishes FELBE from other FEL user facilities is the possibility of delivering a continuous train of (micro)pulses, made possible by the superconducting accelerator cavities. The FEL thus provides picosecond optical pulses at a repetition rate of 13 MHz.

In order to pinpoint interesting scientific experiments using the FEL, one has to focus on its unique features, which are high peak power (up to 1 MW), high average power (tens of Watts), and short pulses (1-20 ps, depending on the wavelength). These features lend themselves to nonlinear optical experiments, near-field microscopy, and time resolved pump-probe studies, respectively. I will present experiments belonging to each of these three classes, namely

(1) pumping the intra-excitonic 1s-2p transition in semiconductor quantum wells, which leads to THz sideband generation and the observation of the AC Stark effect;
(2) near-field micro-spectroscopy of ferroelectrics, which allows imaging of ferroelectric domains in BaTiO3 purely due to their optical contrast resulting from a slight anisotropy of the dielectric function;
(3) carrier relaxation in semiconductor quantum dots. Here the relaxation time varies by three orders of magnitude (2 ps to 1.5 ns), if the energy level spacing is changed by only a factor of two (30 meV to 15 meV).
Keywords: free electron laser, spectroscopy, terahertz
  • Invited lecture (Conferences)
    THz radiation: generation, detection and applications (Heraeus Seminar), 18.-21.04.2010, Bad Honnef, Deutschland

Publ.-Id: 14018 - Permalink


Impulsive terahertz radiation with high electric fields from an amplifier-driven large-area photoconductive antenna
Beck, M.; Schäfer, H.; Klatt, G.; Demsar, J.; Winnerl, S.; Helm, M.; Dekorsy, T.;
We report on the generation of impulsive terahertz (THz) radiation with 36 kV/cm vacuum electric field (1.5 mW average thermal power) at 250 kHz repetition rate and a high NIR-to-THz conversion efficiency of 2×10−3. This is achieved by photoexciting biased large-area photoconductive emitter with NIR fs pulses of μJ pulse energy. We demonstrate focussing of the THz beam by tailoring the pulse front of the exciting laser beam without any focussing element for the THz beam. A high dynamic range of 104 signal-to-noise is obtained with an amplifier based system.

Publ.-Id: 14017 - Permalink


Biosorption of U(VI) by the green algae Chlorella vulgaris in dependence of pH value and cell activity
Vogel, M.; Günther, A.; Rossberg, A.; Li, B.; Bernhard, G.; Raff, J.;
Biosorption of uranium(VI) by the green alga Chlorella vulgaris was studied at varying uranium concentrations from 5 µM to 1 mM, and in the environmentally relevant pH range of 4.4 to 7.0. Living cells bind in a 0.1 mM uranium solution at pH 4.4 within 5 min 14.3 ± 5.5 mg U/g dry biomass and dead cells 28.3 ± 0.6 mg U/g dry biomass which corresponds to 45% and 90% of total uranium in solution, respectively. During 96 h of incubation with uranium initially living cells died off and with 26.6 ± 2.1 mg U/g dry biomass bound similar amounts of uranium compared to dead cells, binding 27.0 ± 0.7 mg U/g dry biomass. In both cases, these amounts correspond to around 85 % of the initially applied uranium. Interestingly, at a lower and more environmentally relevant uranium concentration of 5 µM, living cells firstly bind with 1.3±0.2 mg U/g dry biomass to 1.4±0.1 mg U/g dry biomass almost all uranium within the first 5 min of incubation. But then algal cells again mobilize up to 80% of the bound uranium during ongoing incubation in the time from 48 h to 96 h. The release of metabolism related substances is suggested to cause this mobilization of uranium. As potential leachates for algal-bound uranium oxalate, citrate and ATP were tested and found to be able to mobilize more than 50% of the algal-bound uranium within 24 h. Differences in complexation of uranium by active and inactive algae cells were investigated with a combination of time-resolved laser-induced fluorescence spectroscopy (TRLFS), extended X-ray absorption fine structure (EXAFS) spectroscopy and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Obtained results demonstrated an involvement of carboxylic and organic/inorganic phosphate groups in the uranium complexation with varying contributions dependent on cell status, uranium concentration and pH.
Keywords: sorption, uranium(VI), green algae, TRLFS, EXAFS, ATR-FTIR

Publ.-Id: 14016 - Permalink


Development of a generalized coalescence and breakup closure for the inhomogeneous MUSIG model
Liao, Y.; Lucas, D.; Krepper, E.; Schmidtke, M.;
In the present study we propose new coalescence and breakup closures for the inhomogeneous MUltiple bubble Size Group (MUSIG) model. The major purpose is to consider bubble coalescence and breakup due to different mechanisms in turbulent gas-liquid mixtures and to develop a generally applicable constitutive model for CFD applications. For bubble coalescence the new model includes coalescence due to turbulence, laminar shear, wake entrainment and eddy capture. Bubble breakup mechanisms encompass turbulent fluctuation, laminar shear and interfacial slip velocity. The new model was implemented in the commercial CFD software (CFX-12.0) and applied to the case of turbulent air-water mixtures in a large vertical pipe (DN200). Simulation results for the evolution of bubble size distributions were compared to the standard closure model of Luo and Svendsen (1996), Prince and Blanch (1990) as well as the experimental data of TOPFLOW test facility. Better prediction is accomplished by the proposed new model.
Keywords: new coalescence and breakup closures, the inhomogeneous MUSIG model, upward pipe flow, TOPFLOW facility

Publ.-Id: 14015 - Permalink


Influence of two-phase turbulence models on the bubble coalescence and breakup behavior in bubbly pipe flow
Liao, Y.; Lucas, D.; Krepper, E.;
In poly-disperse bubbly flows, bubble coalescence and breakup are important local events, which determines the evolution of the flow as well as the transition to slug flow. On the other hand side, the characterization of bubble coalescence and breakup is still one weak point in the CFD simulation of poly-disperse bubbly flows, since the transferability of available models is limited. A generalized model was proposed in our previous work, which takes into account all mechanisms of interest for bubble coalescence and breakup. Turbulence is one major mechanism in a turbulent bubbly flow. In other word, the performance of models for bubble coalescence and breakup relies on the accuracy of turbulence modeling. However, two-phase turbulence modeling is still one open issue.

In the current work, air-water bubbly flow in a vertical pipe (DN200) was investigated. The experimental data were obtained from the TOPFLOW test facility at the Forschungszentrum Dresden-Rossendorf (FZD). The inhomogeneous MUSIG approach in CFD code CFX with a new closure model for bubble coalescence and breakup was used for the simulation. Influence of various two-phase turbulence models was studied. The results of bubble size distribution, radial gas volume fraction, air/water axial velocity, Sauter mean bubble diameter as well as turbulent parameters were compared for each model.
In general, a good agreement with the experimental data has been achieved. The new model for bubble coalescence and breakup was shown as capable of predicting the flow evolution. The influence of two-phase turbulence modeling is considerable. Bubble-induced turbulence can be modeled by additional source term for turbulence transport equations instead of additional viscosity term.
Keywords: Poly-disperse bubbly flow, New model for bubble coalescence and breakup, Two-phase turbulence modeling
  • Contribution to proceedings
    The 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8), 10.-14.10.2010, Shanghai, China
  • Lecture (Conference)
    The 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8), 10.-14.10.2010, Shanghai, China

Publ.-Id: 14014 - Permalink


Validierung von Software-Komponenten zur Voraussage der strahleninduzierten Schädigung von RDB-Stahl
Bergner, F.; Birkenheuer, U.; Ulbricht, A.;
Die skalenübergreifende Modellierung der strahleninduzierten Schädigung von RDB-Stahl von den Primärschäden auf der atomaren Skala bis zu den Änderungen der mechanischen Eigenschaften auf der Makroskala trägt wesentlich zu einem ver¬besserten Verständnis des Phänomens der Neutronenversprödung bei. Sie kann sich zukünftig zu einem Bestandteil der Sicherheitsbewertung des RDB entwickeln. Der gewählte zweistufige Modellierungsansatz beruht auf der Kopplung eines ratentheoretischen Moduls zur Voraussage der Größenverteilung der strahlen¬induzierten Defekt-Fremdatom-Cluster mit einem Härtungs-Modul zur Voraussage der strahleninduzierten Streckgrenzenerhöhung. Gegenstand der Untersuchungen sind die Weiterentwicklung und Validierung entsprechender Software-Komponenten. Die Validierung erfolgt durch Gegenüberstellung der Berechnungsergebnisse mit Resultaten von Neutronenkleinwinkelstreumessungen und Zugversuchen an neutronenbestrahlten RDB-Stählen.

Der entwickelte ratentheoretische Modul ermöglicht es, die Größe, Konzentration und Zusammensetzung gemischter Cu-Leerstellen-Cluster über die für RDB-Stähle relevanten Größenbereiche von bis zu 10000 Atomen und Zeitbereiche von bis zu mehreren 10 Jahren zu verfolgen. Die Verbindung der Ratentheorie zur Härtungs¬modellierung beruht auf der Übergabe von berechneten mittleren Hindernis¬abständen und -stärken. Die Validierung der numerischen Werkzeuge hat ergeben, dass wesentliche Tendenzen der strahleninduzierten Streckgrenzenerhöhung von Cu-haltigen und Cu-armen RDB-Stählen richtig wiedergegeben werden. Erste Ansätze zur Erfassung des Einflusses des Legierungselements Nickel im Rahmen der Ratentheorie und der Härtungsmodellierung wurden verwirklicht.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-533 2010
    ISSN: 1437-322X

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Publ.-Id: 14013 - Permalink


Experimental data on steam bubble condensation in poly-disperded upward vertical pipe flow
Lucas, D.; Beyer, M.; Szalinski, L.;
Experiments were done at the TOPFLOW facility of the Forschungszentrum Dresden-Rossendorf to establish a CFD-grade database on the condensation of steam bubbles injected into sub-cooled upwards vertical pipe flow. Bubble condensation has to be considered in Nuclear Reactor Safety Research, e.g. if sub-cooled boiling or bubble entrainment caused by ECC injection occurs. Bubble size distributions are important, since the condensation rate is proportional to the interfacial area density. To develop and validate closure models for CFD codes experimental data with high resolution in space and time are required. The steam was injected via orifices in the pipe wall located at different distances from measuring plane. 1 mm and 4 mm injection orifices are used to vary the initial bubble size distribution. The variation of the distance between the location of the gas injection and the measuring plane allows investigating the evolution of the flow along the pipe. Pressure, steam and water flow rates and the sub-cooling were also varied. Measurements are done using wire-mesh sensors and thermocouples. Data on averaged void fraction, radial gas volume fraction profiles, profiles of the gas velocity and bubble size distributions in dependency of the L/D ratio are available.
Keywords: condensation, phase transfer, bubbles, two-phase flow, CFD
  • Contribution to proceedings
    CFD4NRS-3, International Workshop on Experimental Validation and Application of CFD and CMFD Codes to Nuclear Reactor Safety Issues, Paper 13.1, 14.-16.09.2010, Washington D.C., USA
  • Lecture (Conference)
    CFD4NRS-3, International Workshop on Experimental Validation and Application of CFD and CMFD Codes to Nuclear Reactor Safety Issues, 14.-16.09.2010, Washington D.C., USA

Publ.-Id: 14012 - Permalink


Pre-test CFD simulations on TOPFLOW-PTS experiments with ANSYS CFX 12.0
Apanasevich, P.; Lucas, D.; Höhne, T.;
Pressurized Thermal Shock (PTS) has been identified as one of the most important industrial needs related to nuclear reactor safety. The PTS analysis requires the simulation of the thermal mixing of cold Emergency Core Cooling (ECC) water injected to the cold leg and flowing to the downcomer with the hot coolant, which is present in the primary circuit. The simulation of single-phase and two-phase PTS situations including e.g. stratification of the flow and direct contact condensation is a challenge for CFD methods and requires careful validation against experimental data. In the frame of the NURISP project attempts are made to improve the CFD modelling for two-phase PTS situations. For this purpose, two reference cases with and without mass transfer due the condensation were defined, which are related to the TOPLOW PTS experiments. The present paper focuses on numerical investigations of thermal mixing process in the cold leg and the downcomer using homogeneous and inhomogeneous models for the resolution of momentum equations. Numerical simulations were performed by using the commercial CFD code ANSYS CFX 12.0.
Keywords: Horizontal Stratified Flow, Pressurized Thermal Shock, Direct Contact Condensation, CFD
  • Contribution to proceedings
    CFD4NRS-3, Workshop on Experimental Validation and Application of CFD and CMFD Codes to Nuclear Reactor Safety Issues, 14.-16.09.2010, Washington D.C., USA
  • Lecture (Conference)
    CFD4NRS-3, Workshop on Experimental Validation and Application of CFD and CMFD Codes to Nuclear Reactor Safety Issues. Paper 11.1, 14.-16.09.2010, Washington D.C., USA

Publ.-Id: 14011 - Permalink


Evaluation of a multichannel-plate PMT as potential timing detector suitable for positron lifetime measurements
Kosev, K.; Butterling, M.; Anwand, W.; Cowan, T.; Hartmann, A.; Heidel, K.; Jungmann, M.; Krause-Rehberg, R.; Massarczyk, R.; Schilling, K. D.; Schwengner, R.; Wagner, A.;
This paper focuses on the evaluation of a multichannel-plate photomultiplier tube (MCP-PMT) as a candidate detector, suitable for positron lifetime studies. Several properties of MCP-PMTs, such as their fast time response, compact size, low susceptibility to magnetic fields, relatively high gain and the low power consumption make them attractive for the positron lifetime spectroscopy. The preliminary tests were performed with the 85001-501 Burle Planacon$^{TM}$ photomultiplier tube assembly. Initial measurements were conducted with a pulsed Picosecond Injection Laser (PiLas) system. The engineering sample of the 85001 exhibits a transit-time-spread (TTS) of 110 ps (FWHM). Further timing experiments showing the suitability of the device as Cherenkov detector are presented. For the first time, a conventional positron lifetime spectrum of Cz-Si probe measured with a spectrometer, where a MCP-PMT detector is incorporated has been demonstrated.
Keywords: multichannel plate detector, photocathode, positron lifetimes
  • Nuclear Instruments and Methods in Physics Research A 624(2010)3, 641-645

Publ.-Id: 14010 - Permalink


How to get a new accelerator mass spectrometry (AMS) facility running: The chemistry part
Merchel, S.; Arnold, M.; Aumaître, G.; Bourlès, D.; Braucher, R.;
The AMS business is booming: Many low-energy (< 1 MV) facilities, which are fully dedicated for 14C-analysis, are under construction or in funding status. Additionally, medium-energy accelerators such as the British 5 MV-NEC machine at “SUERC” Glasgow, the French 5 MV-HVEE-machine “ASTER” at Aix-en-Provence [2] and the two German 6 MV-HVEE-machines “DREAMS” at Dresden [3] and “Cologne AMS” at Cologne [4] have been recently installed or are still in testing mode in Central Europe. Of course, these bigger machines need not only experienced physicists and technicians to get them running. It also seems to be advisable to have some experienced scientists around, who knows how to prepare AMS targets for 10Be, 26Al, 36Cl, 41Ca, and 129I measurements.
In contrast to the 14C-community, where e.g. round-robin exercises are routine business, the idea of quality assurance and traceable standards has only been brought up lately for the other cosmogenic radionuclides measurable at medium-energy AMS facilities. Thus, world-wide accepted standards issued by metrology institutes are rare: NIST is selling two kinds of 129I/127I-standards, and the Institute for Reference Materials and Measurements (IRMM) provides one set of 41Ca/40Ca solutions having eight different ratios [5]. Unfortunately, the most commonly used 10Be/9Be standard provided by NIST has been recently sold-out and will not be reissued. Other primary standard-type materials (26Al,36Cl), which are not commercially available, have been prepared by diluting certified activities and subsequent analysis within round-robin exercises [6-8]. After production of big quantities of in-house secondary standards for all nuclides (Tab. 1), cross-calibration versus primary standard-type materials has to be performed [2].

Table 1: Primary and secondary AMS standards in use at ASTER and DREAMS.
Primary standards Secondary (in-house) standards
10Be NIST SRM 4325 (sold-out) NIST SRM 4325 (ASTER)
10Be via 9Be(nth,gamma)10Be (DREAMS)
26Al MB04-A,B,C,D [6] SM-Al-10,11,12,13 [2]
36Cl SM-Cl-11,12,13 [7,8] SM-Cl-11,12,13 [7,8]
41Ca IRMM ERM®-AE701 [5] SM-Ca-10,11,12 [2]
--> SM-Ca-P9,11,13 [2]
129I NIST SRM 3231, Level II SM-I-9,10,11,12

Finally, as commercial 9Be contains intrinsic 10Be up to a level of 4x10-14 [9] sophisticated production of in-house carriers, used as machine blanks and for samples, from Be-containing minerals such as Be2SiO4 originating from deep mines, is needed. After production and measurement of all these materials, the AMS facility is ready for routine measurements.

Acknowledgments: We are grateful to U. Herpers & E. Strub for providing 26Al-activity, to A. Wallner & M. Bichler for performing the neutron-irradiation of 9Be, to C. Varajão for providing Be2SiO4 crystals, and to R.C. Finkel, L. Benedetti, W. Möller, HVEE, the FZD-operator- & AMS-team for great cooperation.

References: [1] S. Freeman et al., NIM B 259 (2007) 66. [2] M. Arnold et al., doi: 10.1016/ j.nimb.2010.02.107. [3] Sh. Akhmadaliev et al., this meeting. [4] M. Klein et al., this meeting. [5] C. Hennessy et al., NIM B 229 (2005) 281. [6] S. Merchel, W. Bremser, NIM B 223–224 (2004) 393. [7] S. Merchel et al. Geochim. Cosmochim. Acta 73 (2009) A871. [8] S. Merchel et al., in prep. for NIM B. [9] S. Merchel et al., NIM B 266 (2008) 4921.
Keywords: accelerator mass spectrometry
  • Poster
    10th European Conference on Accelerators in Applied Research and Technology (ECAART 10), 13.-17.09.2010, Athens, Greece

Publ.-Id: 14009 - Permalink


Prokaryotic microorganisms in uranium mining waste piles and their interactions with uranium and other heavy metals
Geißler, A.;
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2007
    Dissertation
    190 Seiten

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Publ.-Id: 14008 - Permalink


Lambda-p femtoscopy in collisions of Ar+KCl at 1.76 AGeV
Agakishiev, G.; Balanda, A.; Bassini, R.; Belver, D.; Belyaev, A. V.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Díaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O. V.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; González-Díaz, D.; Guber, F.; Hennino, T.; Holzmann, R.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krizek, F.; Krücken, R.; 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.; Mishra, D.; Morinière, E.; Mousa, J.; Müntz, C.; Naumann, L.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wendisch, C.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y. V.; Zhou, P.; Zumbruch, P.;
Results on Lambda p femtoscopy are reported at the lowest energy so far. At a beam energy of 1.76A~GeV, the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. A high-statistics and high-purity Lambda sample was collected, allowing for the investigation of Lambda p correlations at small relative momenta. The experimental correlation function is compared to corresponding model calculations allowing the determination of the space-time extent of the Lambda p emission source. The Lambda p source radius is found slightly smaller than the pp correlation radius for a similar collision system. The present Lambda p radius is significantly smaller than that found for Au+Au/Pb+Pb collisions in the AGS, SPS and RHIC energy domains, but larger than that observed for electroproduction from He. Taking into account all available data, we find the Lambda p source radius to increase almost linearly with the number of participants to the power of one-third.

Publ.-Id: 14007 - Permalink


Spektroskopische Charakterisierung eines ternären U(VI)-Carbonato-Humat-Komplexes mittels ATR FT-IR und cryo-TRLFS
Steudtner, R.; Schmeide, K.; Sachs, S.; Müller, K.;
Die Komplexierung zwischen Uran(VI) und Huminsäure (HA) in Gegenwart von Carbonat wurde mittels abgeschwächter Totalreflexion Fourier-Transform Infrarotspektroskopie (ATR FT-IR) und zeitaufgelöster laserinduzierter Fluoreszenzspektroskopie bei tiefen Temperaturen untersucht. Die Bildung eines ternären U(VI)-Carbonato-Humat Komplexes konnte spektroskopisch nach gewiesen werden. Die in dieser Arbeit bestimmten Komplexbildungskonstanten von log K(I=0,1M) = 2,69 ± 0,47 (cryo-TRLFS) und log K(I=0,1M) = 3,14 ± 0,70 (ATR FT-IR) zeigen eine sehr gute Übereinstimmung.
Keywords: Uran(VI), Huminsäure, ATR FT-IR, cryo-TRLFS
  • Lecture (Conference)
    Workshop zum Verbundprojekt „Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika“, 13.-14.04.2010, Dresden, Deutschland

Publ.-Id: 14006 - Permalink


Measurement of liquid distributions in particle packings: use of wire mesh sensor versus transmission tomographic imaging
Bieberle, A.; Schubert, M.; Da Silva, M. J.; Hampel, U.;
The paper compares two different high-resolution imaging techniques for the investigation of the hydrodynamics in a laboratory packed bed reactor operating at different stationary states and with two different particle packings. The wire-mesh sensor offers cross-sectional liquid holdup distribution imaging at ultra high speed of 10,000 frames per second and good spatial resolution. It is therefore a very useful imaging tool for transient and periodic flow conditions. But yet its influence on the flow in a packed bed was never analyzed. Gamma-ray computed tomography uses 662 keV gamma photons to obtain cross-sectional phase distribution images. It offers as well a good spatial resolution of 2 mm and does not influence the flow. But it needs rather long scanning times. As a non-invasive technique gamma-ray tomography has been used as a reference modality to evaluate the wire-mesh sensor measurements. Data from both imaging modalities are compared utilizing different analyzing models and showed good agreement. For the wire mesh sensor only marginal intrusive effects with respect to the flow dynamics were found.
Keywords: wire-mesh sensor, gamma-ray tomography, packed bed reactor
  • Industrial & Engineering Chemistry Research 49(2010)19, 9445-9453
    DOI: 10.1021/ie100900g

Publ.-Id: 14005 - Permalink


Möglichkeiten und Potentiale einer modernen Faserstoffherstellung
Tobisch, S.; Krug, D.; Mäbert, M.; Bieberle, A.;
Die Herstellung von Holzfaserstoffen im Druckrefiner stellt einen hoch komplexen Prozess dar, dessen Wirkungsweise und entsprechende physikalische Zusammenhänge bisher Zeitpunkt nur in geringem Maße beschrieben sind. Momentan werden Holzfaserstoffe in ausreichender Qualität unter enormem Energieeinsatz produziert, wobei sich jedoch eine gezielte Einstellung und Messung der Faserqualität als schwierig gestaltet. Das Potential, dass die umfassende theoretische Durchdringung des Zerfaserungsprozesses und die sich daraus ergebenden Optimierungsmöglichkeiten hinsichtlich Einstellung einer definierten Faserqualität und Energieeinsparung bietet, wird nicht ausgeschöpft. Die vorliegende Arbeit befasst sich daher mit der Ist-Stand-Analyse des thermomechanischen Faserstoffaufschlusses und macht die Abbildung der thermodynamischen Prozesse, des Materialflusses und der Energieaufnahme während der Zerfaserung möglich.
Keywords: Refiner, Gamma-CT
  • Contribution to proceedings
    14. Holztechnologisches Kolloquium - Werkstoffe aus Holz und Holzverarbeitung im Fokus von Forschung und Entwicklung, 08.-09.04.2010, Dresden, Deutschland
    Möglichkeiten und Potentiale einer modernen Faserstoff-herstellung

Publ.-Id: 14004 - Permalink


Untersuchungen zur Am(III)-Komplexierung durch Modellliganden, zur Np(V)-Reduktion durch schwefelhaltige Huminsäuren sowie zur pH-abhängigen U(VI)-Sorption an Opalinuston unter aeroben und anaeroben Bedingungen
Raditzky, B.; Schmeide, K.; Sachs, S.; Joseph, C.; Frost, L.; Bernhard, G.;
Im Vortrag werden Ergebnisse zur spektroskopischen Bestimmung von Stabilitätskonstanten für die Am(III)-Komplexierung durch organische Modellliganden sowie zur temperaturabhängigen Untersuchung der U(VI)-Humat-Komplexierung präsentiert. Desweiteren wird der Einflusses von Schwefelfunktionalitäten auf die Np(V)-Reduktion durch Huminsäuren diskutiert. Weiterhin werden neue Erkenntnisse zur pH-abhängigen U(VI)-Sorption an Opalinuston unter anaeroben und aeroben Bedingungen vorgestellt.
Keywords: Actinides, humic substances, complexation, reduction, functional groups, sorption, opalinus clay
  • Lecture (Conference)
    Workshop zum Verbundprojekt „Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika“, 13.-14.04.2010, Dresden, Deutschland

Publ.-Id: 14003 - Permalink


Solar fusion cross sections II: the pp chain and CNO cycles
Adelberger, E. G.; Balantekin, A. B.; Bemmerer, D.; Bertulani, C. A.; Chen, J.-W.; Costantini, H.; Couder, M.; Cyburt, R.; Davids, B.; Freedman, S. J.; Gai, M.; Garcia, A.; Gazit, D.; Gialanella, L.; Greife, U.; Hass, M.; Heeger, K.; Haxton, W. C.; Imbriani, G.; Itahashi, T.; Junghans, A.; Kubodera, K.; Langanke, K.; Leitner, D.; Leitner, M.; Marcucci, L. E.; Motobayashi, T.; Mukhamedzhanov, A.; Nollett, K. M.; Nunes, F. M.; Park, T.-S.; Parker, P. D.; Prati, P.; Ramsey-Musolf, M. J.; Hamish Robertson, R. G.; Schiavilla, R.; Simpson, E. C.; Snover, K. A.; Spitaleri, C.; Strieder, F.; Suemmerer, K.; Trautvetter, H.-P.; Tribble, R. E.; Typel, S.; Uberseder, E.; Vetter, P.; Wiescher, M.; Winslow, L.;
We summarize and critically evaluate the available data on nuclear fusion cross sections important to energy generation in the Sun and other hydrogen-burning stars and to solar neutrino production. Recommended values and uncertainties are provided for key cross sections, and a recommended spectrum is given for 8B solar neutrinos. We also discuss opportunities for further increasing the precision of key rates, including new facilities, new experimental techniques, and improvements in theory. This review, which summarizes the conclusions of a workshop held at the Institute for Nuclear Theory, Seattle, in January 2009, is intended as a 10-year update and supplement to Reviews of Modern Physics 70 (1998) 1265.

Publ.-Id: 14002 - Permalink


Microcavity enhanced silicon light emitting pn-diode
Potfajova, J.; Schmidt, B.; Helm, M.; Gemming, T.; Benyoucef, M.; Rastelli, A.; Schmidt, O. G.;
An electrically driven silicon light emitting diode with two distributed Bragg reflectors is reported. The active material is a Si pn-junction fabricated by boron ion implantation into an n-type silicon-on-insulator wafer. The cavity with a thickness of a few wavelengths is formed by amorphous Si/SiO2 multilayer stacks. A strong narrowing and enhancement of the electroluminescence at a resonant wavelength of lambda=1146 nm is observed with a quality factor of Q=143 and a finesse of F=11.
Keywords: silicon, light emittter, microcavity, electroluminescence, light emitting diodes

Publ.-Id: 13999 - Permalink


Wisp-like structures in vertical gas-liquid pipe flow revealed by wire mesh sensor studies
Perez, V. H.; Azzopardi, B. J.; Kaji, R.; Da Silva, M. J.; Beyer, M.; Hampel, U.;
A conductance Wire Mesh Sensor system has been employed on a vertical 67 mm diameter pipe with the up flow of air and water mixtures. The measuring system provides time and cross-sectionally resolved information about the spatial distribution of the phases. Statistical information can be extracted and used to identify flow patterns. The fully resolved data has revealed a hitherto unreported structure has been seen in churn flow which could be linked to the wisps in wispy-annular flow.
Keywords: gas-liquid two-phase flow, wire mesh sensor

Publ.-Id: 13998 - Permalink


Post Mortem Investigations of Greifswald WWER-440 Reactor Pressure Vessels
Viehrig, H.-W.; Houska, M.; Arora, K. S.; Rindelhardt, U.;
Nuclear plant operators must demonstrate that the structural integrity of a nuclear reactor pressure vessel (RPV) is assured during routine operations or under postulated accident conditions. The aging of the RPV steels is controlled with surveillance program results. Radiation loading, metallurgical and environmental histories, however, can differ between surveillance and RPV materials. Therefore, the investigation of RPV material from decommissioned NPPs offers the unique opportunity to evaluate the real toughness response. A chance is given now with the investigation of RPV material from the decommissioned Greifswald NPP (WWER-440/230).
The Greifswald RPVs represent different material conditions such as irradiated, irradiated and annealed and irradiated, annealed and re-irradiated. A region covering ±0.70 m above and below the circumferential core weld was recovery annealed at 475° for about 150 hours. The working program is focused on the characterisation of the RPV steels (base and weld metal) through the RPV wall. It comprises chemical analysis, microstructure investigations (by means of metallography, electron microscopy and SANS) and mechanical testing (hardness measurements, tensile, Charpy-V), and fracture mechanics testing. The key part of the testing is focussed on the determination of the reference temperature T0 following the ASTM test standard E1921-09 to determine the facture toughness, and how it degrades under neutron irradiation.
The paper presents test results measured on trepans of the welding seam and base metal located in the reactor core region. The test results comprise Charpy-V, tensile and fracture toughness parameters. An additional aspect is the comparison of results determined on sub-size Charpy specimens machined of templates taken after the annealing from the uncladded inner RPV wall.
Keywords: nuclear reactor, reactor pressure vessel steel, fracture toughness, Master Curve, integrity assessment
  • Contribution to proceedings
    11th International Conference “Material Issues in Design, Manufacturing and Operation of Nuclear Power Plants Equipment, 14.-18.06.2010, St. Petersburg, Russia
    Proceedings of the 11th International Conference Material Issues in Design, Manufacturing and Operation of Nuclear Power Plants Equipment, St. Petersburg
  • Lecture (Conference)
    11th International Conference “Material Issues in Design, Manufacturing and Operation of Nuclear Power Plants Equipment, 14.-18.06.2010, St. Petersburg, Russia

Publ.-Id: 13997 - Permalink


Modified automated synthesis of sodium 2-[18F]fluoroacetate using a TracerlabFXN synthesizer.
Kniess, T.; Richter, S.; Steinbach, J.;
1. Introduction:
Prostate cancer is the most frequently diagnosed cancer in men over the age of 40 years in Europe and the USA and its early detection is crucial for prognosis and outcome of the disease. Besides the established radiotracers based on 11C- and 18F-labeled choline [11C]acetate is used for the early detection of prostate cancer and its recurrence. 2-[18F]Fluoroacetate has been proposed as alternative to [11C]acetate offering the advantage of longer half-life which facilitates synthesis, shipping and allowing longer imaging protocols. A few radiosyntheses of the radiotracer have been published in the past, mainly based on trapping of the 2-[18F]fluoroacetate ethylester on C18 cartridges (Oasis HLB), followed by acidic hydrolysis [1-3]. Our approach is the fully automated synthesis of 2-[18F]fluoroacetate with a TracerlabFXN synthesizer including separation of the radiotracer via anion exchange cartridges in alkaline solution.

2. Materials and methods:
The radiolabeling with [18F]fluoride was performed with 2-methanesulfonyl-acetic acid t-butyl-ester as precursor in acetonitrile at 100°C. After hydrolysis with 1M HCl and addition of 1M NaOH the alkaline reaction mixture was diluted with 20mL of water and passed through a combination of two anion exchange cartridges where 2-[18F]fluoroacetate was trapped. The 2-[18F]fluoroacetate was recovered by elution with NaHCO3 and excess [18F]fluoride was removed by alumina N cartridges to provide radiochemical pure sodium 2-[18F]fluoroacetate (radio-TLC, RP18, acetonitrile/water=85/15; Rf=0.59).

3. Results:
The radiosynthesis of sodium 2-[18F]fluoroacetate was accomplished with a TracerlabFXN synthesizer by a fully automated procedure. The purification of the product was performed by anion exchange cartridges and gave the radiotracer in 27-30% yield (decay-corrected) and 99% radiochemical purity within 30 min total synthesis time.

4. Discussion/Conclusion:
The modified approach of radiosynthesis and purification delivers sodium 2-[18F]fluoroacetate in high radiochemical purity and good radiochemical yield. The improved radio-TLC method using RP18 plates represents an easy system to distinguish [18F]fluoride from 2-[18F]fluoroacetate. Further optimization of this new method utilising a new precursor and a modified separation system is in progress. The conformation of the process to GMP requirements will be performed in the near future.

References:
[1] Sun LQ, Mori T, Dence CS, Ponde DE, Welch MJ, Furukawa T, Yonekura Y, Fujibayashi Y, [2006], Nucl.Med.Biol., 33:153-158
[2] Ponde DE, Dence CS, Oyama N, Kim J, Tai YC, Laforest R, Siegel BA, Welch MJ, [2007], J.Nucl.Med., 48(3): 420-428
[3] Marik J, Ogasawara A, McNulty BM, Ross J, Flores JE, Gill HS, Tinianow JN, Vanderbilt AN, Nishimura M, Peale F, Pastuskovas C, Greve JM, van Bruggen N, Williams SP, [2009], J.Nucl.Med., 50(6): 982-990
  • Poster
    15th European Symposium on Radiopharmacy and Radiopharmaceuticals (ESRR), 08.-11.04.2010, Edinburgh, Großbritannien
  • Abstract in refereed journal
    Quarterly Journal of Nuclear Medicine and Molecular Imaging 54(2010)S1, 54

Publ.-Id: 13996 - Permalink


Dose dependent biological damage of tumour cells by laser-accelerated proton beams
Kraft, S. D.; Richter, C.; Zeil, K.; Baumann, M.; Beyreuther, E.; Bock, S.; Bussmann, M.; Cowan, T. E.; Dammene, Y.; Enghardt, W.; Helbig, U.; Karsch, L.; Kluge, T.; Laschinsky, L.; Lessmann, E.; Metzkes, J.; Naumburger, D.; Sauerbrey, R.; Schürer, M.; Sobiella, M.; Woithe, J.; Schramm, U.; Pawelke, J.;
We report on the irradiation of in vitro tumour cells with laser-accelerated proton pulses showing dose dependent biological damage. This experiment, paving the way for future radiobiological studies with laser-accelerated protons, demonstrates for the first time the simultaneous and reliable availability of all components indispensable for systematic radiobiological studies: A laser-plasma accelerator providing stable proton spectra with maximum energy exceeding 15 MeV and applicable doses of a few Gy within few minutes, a beam transport and filtering system, an in-air irradiation site, a dedicated dosimetry system providing both online dose monitoring and a precise absolute dose information applied to the cell sample, and the full infrastructure for analysing radiation induced damage in cells.

Publ.-Id: 13995 - Permalink


Theoretical investigations of carbon-based nanocoatings
Kunze, T.; Gemming, S.; Posselt, M.; Erdogan, E.; Seifert, G.;
Nanocoatings have the potential to improve the surface characteristics of various materials. They are of extreme importance for surfaces in sliding contact such as highly stressed engine parts. Here, nanocoatings have to be optimized with respect to low friction properties and a high wear resistance to enhance the energetic and environmental efficiency. Our research activity focuses on self-lubricating and hard cabon-based nanocoatings (C:TM and taC films) investigated by atomic-scale simulations. We will present morphological as well as tribological properties of the studied systems. Support by the European Union and the Freistaat Sachsen via SAB project 13857/2379 within the ECEMP initiative is gratefully acknowledged.
  • Lecture (Conference)
    Nanocoatings 2010, 28.-31.03.2010, Dresden, Deutschland

Publ.-Id: 13994 - Permalink


Crystalline ripples at the surface of ion eroded strained Si0.8Ge0.2 epilayers
Kanjilal, A.; Prucnal, S.; Minniti, M.; Skorupa, W.; Helm, M.; Facsko, S.;
Surface erosion of a strained Si0.8Ge0.2 epilayer by 500 eV Ar+ ions with a fluence of 4 x1017 ions/cm2 and the transformation from crystalline ripples to elongated Ge islands are reported by aligning the beam from 69° to 50° from the surface normal. Crystalline nature and the near surface Ge enrichment in such ripple structures are revealed by transmission electron microscopy. Moreover, ion beam induced decomposition of the SiGe network and the appearance of dislocation bands by suppressing the near-bandgap emission are manifested by u-Raman and photoluminescence studies, respectively.
Keywords: SiGe, ripples, photoluminescence, Raman
  • Journal of Applied Physics 107(2010), 073513

Publ.-Id: 13993 - Permalink


Wie flexibel ist die Einwirkzeit von 18F-NaF
May, C.; Beuthien-Baumann, B.; Oehme, L.; Kotzerke, J.;
Ziel/Aim:
Bedingt durch die bestehende Knappheit an 99m-Technetium wurden vermehrte Skelettszintigraphien mit 18F-Natriumfluorid (18F-NaF) am PET-Scanner (Siemens HR+) durchgeführt. Es sollte untersucht werden, wie flexibel die Einwirkzeit des 18F-NaF in der Routine gehandhabt werden kann, ohne die Bildqualität negativ zu beeinflussen.

Methodik/Methods:
Der PET-Scan wurde in 3D-Listmode-Technik aufgenommen, 360 MBq 18F-NaF, Emissionsdauer von 4 min pro Bettposition, keine Schwächungskorrektur. Der Abstand von Injektion von 18F-NaF zum Untersuchungssbeginn betrug in der ersten Gruppe 40-60 min, in der 2. Gruppe 60-80 min, in der 3.Gruppe 80-120 min. Bislang wurden 10 Patienten pro Gruppe ausgewertet. Es wurden standardisierte Regions of interest über Lunge und LWK1 (bzw LWK 2 oder BWK 12 gelegt, falls bei LWK 1 eine pathologische Mehranreicherung erkennen ließ) und Quotienten aus Anreicherung in LWK und Lunge gebildet.

Ergebnisse/Results:
Qualitativ konnten alle Patienten ausgewertet werden. Der Mittelwert der Quotienten aus LWK/Lunge betrug für die Gruppe 40-60 min p.i. 2,4; für die Gruppe 60-80 min p.i. 2,3 und für die Gruppe 80-120 min p.i. 3,0. Zwischen Gruppe 1 und 2 bestand hinsichtlich der LWK/Lunge-Quotienten kein wesentlicher Unterschied. Der Mittelwert für die Gruppe 3 lag mit 3,0 etwas höher, unterschied sich jedoch statistisch nicht signifikant von Gruppe 1 und 2.

Schlussfolgerungen/Conclusions:
Nach 40 min ist ohne weiteres eine Aufnahme mit 18F-Fluorid mit guter Bildqualität möglich. Unsere Berechnungen haben ergeben, dass bei einer Einwirkzeit zwischen 40 -80 min keine wesentlichen Qualitätsunterschiede zu erwarten sind. Dadurch fügt sich die Skelettaufnahme am PET flexibel in den Tagesablauf ein. Einen möglichen Gewinn an Bildqualität nach 80-120 min sollte man sich bei adipösen Patienten zu nutze machen.
  • Poster
    48. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 21.-24.04.2010, Leipzig, D
  • Abstract in refereed journal
    Nuklearmedizin 49(2010)2, A113

Publ.-Id: 13992 - Permalink


Wie weit bewegen sich die Schwerpunkte hypoxischer Tumorsubvolumina von HNO-Tumoren unter kombinierter Radiochemotherapie.
Abolmaali, N.; Zöphel, K.; Koch, A.; Haase, R.; Steinbach, J.; Baumann, M.;
Ziel/Aim:
Die Berücksichtigung hypoxischer Tumorsubvolumina anhand von FMISO-Daten zur Strahlentherapieplanung ist aufgrund des geringen Signal-zu-Rausch-Verhältnisses schwierig, weil die Konturen nicht eindeutig definiert sind. Ziel dieser Untersuchung war darzustellen, wie weit sich die Schwerpunkte Wie weit wandern die Schwerpunkte hypoxischer Tumorsubvolumina unter kombinierter Radiochemotherapie bewegen.

Methodik/Methods:
14 Patienten (2@, medianes Alter 55 Jahre) mit Plattenepithelkarzinomen des HNO-Traktes wurden vor kombinierter Radiochemotherapie (RCT) mit FDG sowie vor und nach 10Gy, 20Gy und 60Gy unter RCT mit FMISO untersucht (56 Untersuchungen). Mit der Rover-Software (ABX, Radeberg) wurde anhand der co-registrierten Daten Kontrast-basiert in jeder Untersuchung ein hypoxisches Tumorsubvolumen definiert und dessen Schwerpunkt im Koordinatensystem bestimmt. Die Bewegung dieses Schwerpunktes im Raum wurde unter RCT vermessen.

Ergebnisse/Results:
Im Mittel bewegen sich die Tumoren von der ersten zur zweiten Untersuchung um 5.6 mm, von der zweiten zur dritten Untersuchung um 5.5 mm und von der dritten zur vierten Untersuchung um 8 mm. Zwischen erster und vierter Untersuchung bewegten sich die Tumoren um 8.8 mm am weitesten. Die durchschnittliche Verschiebung des Schwerpunktes unter RCT lag bei 6.4 mm.

Schlussfolgerungen/Conclusions:
Unter Berücksichtigung der Registrierungsgenauigkeit von 2 mm und der maximalen Schwerpunktsbewegung von 9 mm erfasst der Strahlentherapieplan am Ende der Therapie das mit FMISO primär geplante Zielvolumen noch vollständig, wenn die üblichen Sicherheitsabstände berücksichtigt werden.
  • Poster
    48. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 21.-24.04.2010, Leipzig, D
  • Abstract in refereed journal
    Nuklearmedizin 49(2010)2, A80

Publ.-Id: 13991 - Permalink


Für die Analyse hypoxischer Tumorvolumina sind 4h-FMISO-Aufnahmen besser geeignet als 2h-FMISO-Aufnahmen.
Abolmaali, N.; Zöphel, K.; Koch, A.; Zips, D.; Steinbach, J.; Baumann, M.;
Ziel/Aim:
Die F-18-Misonidazol-PET (FMISO) zur Detektion hypoxischer Tumorsubvolumina weist ein vergleichsweise geringes Signal-zu-Rausch-Verhältnis auf. Üblicherweise werden neben der Dynamik Aufnahmen nach 2h und 4h p.i. angefertigt. Ziel dieser Untersuchung war es zu entscheiden, welche der beiden Spätaufnahmen den besten Kontrast hat und damit am besten für Volumenanalysen geeignet ist.

Methodik/Methods:
25 Patienten (3@, medianes Alter 55 Jahre) mit Plattenepithelkarzinomen des HNO-Traktes wurden vor kombinierter Radiochemotherapie (RCT) mit FDG sowie vor und nach 10Gy, 20Gy und 60Gy unter RCT mit FMISO untersucht (66 Untersuchungen). Mit der Rover-Software (ABX, Radeberg) wurde nach Co-Registrierung der PETs mit dem halbautomatischen Source-to-Background-Algorithmus anhand der FDG-Daten das Tumorgesamtvolumen definiert und in die FMISO kopiert. In diesem Tumorvolumen wurde die MISO-Aktivität bestimmt. Zusätzlich wurde in jeder FMISO ein 5-10 ml großes Referenzvolumen zur Definition des Hintergrundsignals von MISO in der Halsmuskulatur als definiert. Der Kontrast wurde mit dem Verhältnis MISO-Aktivität im Tumor zu MISO-Aktivität im Hintergrund bestimmt. Der statistische Vergleich erfolgte mit dem Wilcoxon-matched-pairs Test.

Ergebnisse/Results:
Der mittlere SUVmax im Tumor nach 2h war 1.9, nach 4h 2.3, der mittlere SUVmean in der Halsmuskulatur nach 2h war 1.2 und nach 4h 1.1. Der Mittelwert±Standardabweichung für den Kontrast nach 2h war 1.33±0.28 und nach 4h 1.41±0.32. Mediane, Minima und Maxima für den Kontrast lagen nach 2h bei 1.29, 0.81 und 2.06 und nach 4h bei 1.38, 0.90 und 2.33. Der Wilcoxon-matched-pairs Test ergab einen hoch signifikanten Unterschied für die Kontraste zwischen diesen beiden Untersuchungszeitpunkten (p = 0.000052).

Schlussfolgerungen/Conclusions:
Für Volumenanalysen von FMISO, z.B. für die Strahlentherapieplanung sind 4h-Daten besser geeignet als 2h-Daten.
  • Poster
    48. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 21.-24.04.2010, Leipzig, D
  • Abstract in refereed journal
    Nuklearmedizin 49(2010)2, A80

Publ.-Id: 13990 - Permalink


> 65 MeV Protons From Laser-Micro-Cone Target Interactions
Gaillard, S. A.; Flippo, K. A.; Gautier, D. C.; Kline, J. L.; Offermann, D.; Workman, J.; Archuleta, F.; Gonzales, R.; Hurry, T.; Johnson, R. P.; Letzring, S.; Montgomery, D. S.; Reid, S.-M.; Shimada, T.; Lockard, T.; Sentoku, Y.; Mucino, J. E.; Lowenstern, M. E.; Gall, B. B.; D’Humières, E.; Cowan, T. E.; Bussman, M.; Kluge, T.; Rassuchine, J.;
We have conducted two sets of laser-ion acceleration experiments at the LANL 200 TW Trident short-pulse laser at ~1020 W/cm2 (1 μm, 80-100 J and ~600 fs) at high (>1010) and low (>108) contrast, comparing regular size flat foils (~2 mm by 2 mm), reduced mass targets (200 μm to 500 μm diameter) and new Cu micro-cone targets in three separate geometries (flat-top or pizza-top, funnel, and snub-nose) to elucidate the production of hot electrons [1] and ions in these targets.
Results from the latest experiment show proton energies in excess of ~65 MeV for the pizza-top cones, compared to ~55 MeV for reduced mass targets and ~45 MeV for regular flat foils for high contrast. Data from a Cu Kα 2D imaging crystal, an X-ray single hit CCD, proton beam images on RCF film stacks, and an electron/proton spectrometer are presented and compared, showing the importance of not just generating hot electrons, but in the case of ion acceleration, efficiently propagating these hot electrons to the accelerating “tip”, where they can then be efficiently converted to ion energy, as well as the importance of the micro-cones’ supporting foil size.
  • Lecture (Conference)
    51st Annual Meeting of the APS Division of Plasma Physics, 02.-06.11.2009, Atlanta, USA

Publ.-Id: 13989 - Permalink


Verlaufsbeobachtung der Hypoxie anhand von FMISO-Untersuchungen in HNO-Tumoren unter kombinierter Radiochemotherapie.
Abolmaali, N.; Zöphel, K.; Koch, A.; Appold, S.; Steinbach, J.; Baumann, M.;
Ziel/Aim:
Zur Optimierung/Individualisierung der Strahlentherapie könnte die Detektion und Berücksichtigung hypoxischer Tumorsubvolumina im Therapieverlauf wichtig sein. Ziel dieser Untersuchung war darzustellen, wie sich in Tumoren die Hypoxie im Vergleich zum nicht im primären Zielvolumen gelegenen Normalgewebe verändert.

Methodik/Methods:
25 Patienten (3@, medianes Alter 55 Jahre) mit Plattenepithelkarzinomen des HNO-Traktes wurden vor kombinierter Radiochemotherapie (RCT) mit FDG sowie vor und nach 10Gy, 20Gy und 60Gy unter RCT mit FMISO untersucht (66 Untersuchungen). Mit der Rover-Software (ABX, Radeberg) wurde nach Co-Registrierung der PETs mit dem halbautomatischen Source-to-Background-Algorithmus anhand der FDG-Daten das Tumorgesamtvolumen definiert und in die FMISO kopiert. In diesem Tumorvolumen wurde die MISO-Aktivität bestimmt. Zusätzlich wurde in jeder FMISO ein 5-10 ml großes Referenzvolumen zur Definition des Hintergrundsignals von MISO in der Halsmuskulatur definiert. Bestimmt wurden im Verlauf der SUVmax, das hypoxische Volumen ("total lesion hypoxia (TLH)" = SUVmean x Volumen) und der Kontrast in Abhängigkeit von der MISO-Aktivität im Hintergrund.

Ergebnisse/Results:
Der gemittelte SUVmax±sd vor, nach 10Gy, nach 20Gy und nach 60Gy lag bei: 2.6±0.6, 2.6±0.7, 2.1±0.6 und 1.6±04. Der SUVmax sank im Mittel auf 64% des Ausgangswertes. Die TLH [ml] vor, nach 10Gy, nach 20Gy und nach 60Gy lag bei: 93.3 ml, 79.6 ml, 77.3 ml und 55.3 ml. Der Kontrast vor, nach 10Gy, nach 20Gy und nach 60Gy lag bei: 1.6±0.3, 1.6±3.9, 1.4±02 und 1.1±0.2. Der Kontrast sank im Mittel auf 71% des Ausgangswertes.

Schlussfolgerungen/Conclusions:
Unter kombinierter Radiochemotherapie sinkt sowohl das Tumorvolumen (erkennbar an den morphologischen CT-Daten) als auch die hypoxische Aktivität der HNO-Tumoren. Da nach 60 Gy der Kontrast in den FMISO-Untersuchungen nahe 1 liegt, lässt sich anhand der aufgenommenen Daten keine Planung für einen Strahlentherapieboost erstellen.
  • Lecture (Conference)
    48. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 21.-24.04.2010, Leipzig, D
  • Abstract in refereed journal
    Nuklearmedizin 49(2010)2, A30

Publ.-Id: 13988 - Permalink


Vorklinische Abschätzung der Strahlenexposition durch (-)-F-18-NCFHEB, einem neuen PET-Tracer zur Darstellung von zerebralen alpha4beta2 nikotinischen Acetylcholinrezeptoren
Sattler, B.; Deuther-Conrad, W.; Fischer, S.; Hiller, A.; Kendziorra, K.; Starke, A.; Patt, M.; Hesse, S.; Smits, R.; Hoepping, A.; Steinbach, J.; Brust, P.; Sabri, O.;
Ziel/Aim:
(-)-F-18-Norchloro-fluoro-homoepibatidin (-)-NCFHEB) ist ein neuer vielversprechender Tracer für die Darstellung von alpha4beta2 nikotinischen Acetylcholinrezeptoren bei neuropsychiatrischen Erkrankungen mit PET. Um die Strahlenexposition durch die Applikation des Tracers abzuschätzen, wurde CD1 Mäusen (-)-NCFHEB appliziert. Es wurden die Biodistribution und die resultierenden Organdosen (OD) sowie die effektive Dosis (ED) bestimmt.

Methodik/Methods:
27 weiblichen CD1 Mäusen (Gewicht: 28,2 ± 2,1g) wurden 0,75± 0,334MBq (-)-F-18-NCFHEB [1] über die V. caudata lateralis appliziert. Nach 5, 15, 30, 45, 60, 90, 120, 180 und 240 min p.i. wurden die Tiere getötet (n=3 pro Zeitpunkt). Die Organe (Hirn, Herz, Lunge, Magen, Dünndarm, Dickdarm, Leber, Nieren, Harnblase, Milz, Thymus, Bauchspeicheldrüse, Nebennieren, Ovarien, Blut, Haut, Muskel, Skelett) wurden isoliert, gewogen und ihr Aktivitätsgehalt in einem g-Counter bestimmt. Die Massen von Skelett und Muskel wurden aus Gewebeproben extrapoliert [2]. Die Zeit- und Massenskalen wurden an die menschlichen Skalen angepasst [3]. Die Aktivitätsanteile in Quellorganen wurden als Fraktionen der injizierten Aktivitätsmenge [%ID] pro Gramm bzw. Organ dargestellt. Mit trapezoiden und exponentiellen Anpassungen an diese Daten wurden Zeit-Aktivitätskurven für jedes Organ bzw. Kompartiment abgeleitet. Die kumulierte Aktivität in den Quellorganen wurden bestimmt und ODs und die ED wurden mit OLINDA abgeschätzt.

Ergebnisse/Results:
Die Harnblase erhält die höchste OD mit 104,0 μSv/MBq, gefolgt von den Nieren (24,2 μSv/MBq), dem Uterus (14,1 μSv/MBq), der Leber (14,0 μSv/MBq) und der Bauchspeicheldrüse (14,0 μSv/MBq). Den höchsten Beitrag zur ED leistet die Harnblase (5,2μSv/MBq) gefolgt von den Ovarien (2,1μSv/MBq), dem Dickdarm (1,5μSv/MBq) und dem roten Knochenmark (1,3 μSv/MBq). Mit diesen Daten ergibt sich die ED durch i.v. Applikation von (-)-F-18-NCFHEB zu 14,2 μSv/MBq.

Schlussfolgerungen/Conclusions:
Die ED durch i.v. Applikation von etwa 370 MBq (-)-F-18-NCFHEB am Menschen ergibt sich zu 5,3 mSv. Dies liegt im Bereich der Strahlenexposition, welche durch andere F-18-markierte Radioliganden erzeugt wird. Diese vorklinischen inkorporationsdosimetrischen Ergebnisse bestärken die weitere Entwicklung von (-)-F-18-NCFHEB in klinischen Studienphasen am Menschen und seine weitere Entwicklung als klinischer Hirn-PET-Tracer.

Literatur/References:
[1] Brust P et. al.: In vivo measurement of nicotinic acetylcholine receptors with [18F]norchloro-fluoro-homoepibatidine (NCFHEB). Synapse 62, 205-218.
[2] Lindstedt SL, Schaeffer PJ.: Use of allometry in predicting anatomical and physiological parameters of mammals Laboratory Animals (2002) 36, 1–19
[3] Stabin MJ: Fundamentals of Nuclear Medicine Dosimetry, Springer 2008, ISBN 978-0-387-74578-7, 237P Diese Studie wird durch das Bundesministerium für Bildung und Forschung unterstützt. (Nr. 01EZ0820)
  • Lecture (Conference)
    48. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 21.-24.04.2010, Leipzig, D
  • Abstract in refereed journal
    Nuklearmedizin 49(2010)2, A66

Publ.-Id: 13987 - Permalink


Proton, Electron and K-Alpha Emission from Micro-Scale Copper Cone Targets
Gaillard, S. A.; Flippo, K. A.; Gautier, D. C.; Kline, J. L.; Offermann, D.; Workman, J.; Archuleta, F.; Gonzales, R.; Hurry, T.; Johnson, R. P.; Letzring, S.; Montgomery, D. S.; Reid, S.-M.; Shimada, T.; Lockard, T.; Sentoku, Y.; D'Humieres, E.; Cowan, T. E.; Bussmann, M.; Kluge, T.; Rassuchine, J.; Mucino, J. E.; Lowenstern, M. E.;
Fast ignition fusion requires transporting a large amount of energy into the compressed ICF capsule in a short period of time. One metthod for efficiently transporting laser energy into a compressed fusion capsule is to use a cone situated near or in the capsule, decreasing the distance to the core, improing laser conversion efficiency and concentrating charged particle flow. Results from recent experiments performed at the LANL 200 TW Trident short-pulse laser at ~1020 W/cm² (80-100 J and ~600 fs) are presented.
Keywords: Cone, Laser, LANL, Trident, Record, Proton, Protons, Energy, Fusion, Acceleration
  • Lecture (Conference)
    IFSA09, 06.-11.09.2009, San Francisco, USA

Publ.-Id: 13986 - Permalink


Erste in-vivo Applikation eines Fluor-18 markierten Serotonin-Transporter-(SERT)-Markers für die PET
Hesse, S.; Brust, P.; Mäding, P.; Bresch, A.; Zessin, J.; Becker, G. A.; Seese, A.; Habermann, B.; Patt, M.; Meyer, P. M.; Luthardt, J.; Steinbach, J.; Sabri, O.;
Ziel/Aim:
Die zentralen SERT lassen sich mittels SPECT-Radiotracern in SERT-reichen Gehirnarealen und mit PET-Markern wie [11C]DASB hochselektiv im gesamten Gehirn darstellen. Die kortikale Test-Retest-Reliabilität von [11C]DASB PET ist lediglich moderat, eine Quantifizierung endogenen Serotonins gelingt mit dieser Methode nicht. Möglicherweise können Tracer mit längerlebigen Nukliden diese Mängel beseitigen helfen. Ziel unserer Studie war die erstmalige Applikation eines Fluor-18-markierten SERT-Radiotracers im Menschen.

Methodik/Methods:
In Anlehnung an (1) wurde die Synthese von [18F]FMe-McN 5652 unter GMP-Bedingungen in einem modifizierten Synthesemodul "TRACERlab FxF-N” als 2-Stufen-2-Topf-Reaktion adaptiert: Stufe 1: Synthese von [18F]Fluormethylbromid durch nukleophile [18F]Fluorierung von Dibrommethan und nachfolgende Reinigung mittels Silicagel-Kartuschen (2). Stufe 2: [18F]Fluormethylierung eines entsprechenden Thiolat-Präkursors. Da [18F]FMe-McN 5652 in wässriger Lösung nicht stabil ist, wurde eine HPLC-Reinigung unter Verwendung eines ethanolischen Eluenten entwickelt, in deren Produktfraktion der Tracer stabil ist. Die PET-Datensätze, erhoben bei 5 gesunden Probanden (2 weiblich, Alter 39±10 Jahre) als dynamische Akquisition über 120 Min. nach i.v. 90-Sek.-Bolusinjektion von 298±57 MBq [18F]FMe-McN 5652 sowie statische Aufnahmen über 30 Min, wurden mit dem individuellen MRT koregistriert (PMOD) und mittels VOI analysiert (Target-/Background-Ratios, TB-R, Background=Zerebellum).

Ergebnisse/Results:
Die TB-R für den frontalen Kortex (FC) betragen 1,02±0,04 für rechts und 1,01±0,03 für links, für die Kaudatuskopfregion (Kaud) 1,46±0,16 (rechts) und 1,50±0,15 (links) und für die RaphÈ-Region 2,04±0,11. Vergleichsweise finden sich bei gesunden Probanden, die mittels [11C]DASB-PET untersucht wurden (N=21, 11 weiblich, 38±8 Jahre), entsprechende TB-R von 1,10±0,07 (FC rechts, t-Test: n.s.), 1,08±0,78 (FC links, n.s.), 2,14±0,21 (Kaud rechts, n.s.), 2,06±0,19 (Kaud links, n.s.) und 2,23±0,39 (RaphÈ, n.s.) bei insgesamt visuell besserer Bildqualität des neuen Tracers.

Schlussfolgerungen/Conclusions:
Die zerebrale [18F]FMe-McN 5652-Aufnahme entspricht der Verteilung der SERT auch beim Menschen, so dass der Radiotracer einen geeigneten Marker für SERT darstellen könnte. Trotz der tendenziell geringeren TB-R im Vergleich mit den [11C]DASB-PET-Daten könnte sich die geringere Standardabweichung bei der Untersuchung der Test-Retest-Reliabilität mit größeren Fallzahlen als Vorteil erweisen. Zudem soll mit Verdrängungsstudien die Sensivitität des neuen Markers, insbesondere in den kortikalen Arealen und hinsichtlich der Quantifizierung endogenen Serotonins, eingeschätzt werden.

Literatur/References:
(1) Zessin J, Eskola O, Brust P et al. Nucl Med Biol 2001; 28: 857-863.
(2) Iwata R, Pascali C, Bogni A et al. Appl Radiat Isot 2002; 57: 347-352
  • Abstract in refereed journal
    Nuklearmedizin 49(2010)2, A34
  • Lecture (Conference)
    48. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 21.-24.04.2010, Leipzig, D

Publ.-Id: 13985 - Permalink


Ein neues stabilisiertes Cu-64 markiertes Neurotensin-Analogon zur in vivo Bildgebung von Neurotensin-Rezeptoren
Bergmann, R.; Brans, L.; Tourwe, D.; Schlottig, K.; Pietzsch, J.;
Ziel/Aim:
Neurotensin (NT) und seine Rezeptoren werden in verschiedenen humanen Tumoren (Brust-, Prostata-, Lungen-, duktale Pankreas- und Hypophysentumore) überexprimiert, insbesondere stehen sie im Zusammenhang mit der Tumorprogression und dem Übergang zu aggressiveren Tumorphänotypen. Deshalb kommt der quantitativen in vivo-Bildgebung der funktionellen Neurotensin-Rezeptor-Expression, sowohl in der Forschung, als auch in Diagnostik und Therapie besondere Bedeutung zu. Deshalb sollte ein in vivo stabiles Neurotensin-Analogon entwickelt werden, das sowohl zur Bildgebung, als auch für therapeutische Zwecke eingesetzt werden kann.

Methodik/Methods:
Durch manuelle Festphasensynthese auf Merrifield-Resin mit anschließender DOTA-Konjugation wurde DOTA-ArgΨ(CH2NH)ArgProDmtTleLeu-OH synthetisiert. Die Markierung des Peptides (3 pmol) mit Cu-64 erfolgte in Ammoniumacetat-Lösung 0,1 M, pH 5.5 über 15 min bei 50&inf;C. Der IC50 wurde an HT-29-Zellen bestimmt. Zellaufnahme und Internalisierung wurden an HT-29- und PC3-Zellen untersucht. Die Bioverteilung des Radiotracers wurde bei HT-29- tumortragenden NMRI-Nacktmäusen sowohl durch Organentnahme (je 4 Tiere pro Zeitpunkt), als auch mit Kleintier-PET (insgesamt 8 Tiere) untersucht. Die Dynamik der Metabolisierung wurde bei Ratten bestimmt.

Ergebnisse/Results:
Die Bindungsaffinität des Peptides an HT-29-Membranen, mit Neurotensin-Rezeptor 1 betrug 7 nM (4-12 nM, 95% Konfidenzintervall). Das Peptid konnte mit einer radiochemischen Reinheit größer 92% in einem Schritt mit Cu-64 markiert werden. Nach einmaliger intravenöser Injektion stieg die Konzentration im Tumor schnell an (0,8±0,1 SUV, 5 min p.i.) und verringerte sich dann auf 0,3±0,1 SUV (60 min p.i.). Daraus ergaben sich Tumor zu Organ-Verhältnisse von 2,8±0,7 im Blut, 5,2±0,9 im Muskel, 4,2±0,6 im Pankreas, 0,6±0,5 in Leber und 0,4±0,4 in Nieren. Das Peptid wurde schnell von den Nieren (3,7±0,6 SUV, 5 min p.i.; 0,8±0,1 SUV 60 min p.i. ) aufgenommen und in den Urin (60±6%ID im Urin nach 1 h) eliminiert . In der PET konnten die xenotransplantierten Tumore deutlich dargestellt werden. Bei gleichzeitiger Injektion von Neurotensin verringerte sich die Tumoraufnahme des Tracers auf 27% der Kontrolle. Nach 1 h lagen noch 33% der Aktivität im Blutplasma der Ratte als Originalsubstanz vor.

Schlussfolgerungen/Conclusions:
Das Cu-64-Neurotensin-Analogon erlaubt auf Grund seiner Stabilität, Affinität und Spezifität die bildgebende Darstellung der funktionellen Expression von Neurotensin-Rezeptoren in vivo. Die Daten lassen erwarten, dass ähnliche Ergebnisse auch mit Radionukliden für SPECT (In-111) oder therapeutische Anwendungen (Cu-67, Lu-177, Y-90) erreicht werden können.

Literatur/References:
Das Projekt wurde partiell durch das EU-Projekt GIPIO (Grant Agreement Nr. 223057) gefördert.
  • Lecture (Conference)
    48. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 21.-24.04.2010, Leipzig, D
  • Abstract in refereed journal
    Nuklearmedizin 49(2010)2, A17

Publ.-Id: 13983 - Permalink


Markierung und Stabilität von DOTA Mikrosphären markiert mit Ga-68, Y-90 und Lu-177
Wunderlich, G.; Schiller, E.; Bergmann, R.; Pietzsch, H.-J.; Kotzerke, J.;
Ziel/Aim:
Intraarteriell applizierbare Partikel, markiert mit therapeutisch wirksamen Radionukliden (Y-90, Lu-177, Re-188) sind eine Alternative zur Behandlung von Lebertumoren und Lebermetastasen. Ga-68 markierte Partikel könnten zur Blutflussdarstellung und zur Lungenperfusion verwendet werden. In unserer Untersuchung verwendeten wir 20μm HSA Mikrosphären (MS). Es wurde untersucht, unter welchen Bedingungen sich DOTA modifizierte MS markieren lassen und wie stabil die Markierungen in vitro und in vivo sind.

Methodik/Methods:
Markiert wurde 1mg MS in 0,5M Azetatpuffer bei pH5, Reaktion 15min bei 95&inf;C unter Schütteln mit 0,1-0,5GBq Ga-68, 0,1-7,2GBq Y-90 und 1,8GBq Lu-177. Die Ausbeuten und die in vitro Stabilität wurden mit ITLC und nach Zentrifugieren bestimmt. Nach Zugabe von 1ml 0,1M DTPA Lösung (Challenge), 20mg Ascorbinsäure (Radikalfänger) und Stehenlassen der Suspension bestimmten wir die in vitro Stabilität der Produkte nach einigen Stunden bis Tagen in Gegenwart von DTPA/Ascorbinsäure bzw. Plasma und die in vivo Stabilität der Y-90 DOTA-MS nach intravenöser Injektion in Wistar-Ratten.

Ergebnisse/Results:
Die Markierungsausbeuten betrugen bei allen Nukliden >90%. Zur Bestimmung der in vitro Stabilitäten wurde das Produkt zentrifugiert und der Überstand abgenommen und/oder nach Aufschütteln eine Dünnschichtchromatografie durchgeführt. Nach 3h Inkubation in Humanplasma wurde 5% Ga-68 im Überstand gefunden. Nach Ascorbinsäurezugabe zum Reaktionsansatz fanden sich 18% freies Lu-177 nach 7d. Bei Y-90 DOTA MS wurden in Gegenwart von Ascorbinsäure bei Markierungen im GBq-Bereich im Überstand der Partikelsuspension unmittelbar nach Markierung bereits >10% der Radioaktivität nachgewiesen. Dabei handelt es sich wahrscheinlich um Y-90 DOTA-Thioharnstoffderivate, die vermutlich in Folge von Radiolyse und erhöhter Temperatur von den Partikeln abgespalten werden. Die Halbwertszeit von Y-90 DOTA-MS in der Lunge nach i.v. Injektion der Partikel in Wistarratten beträgt 3,5d.

Schlussfolgerungen/Conclusions:
Die Stabilität der Ga-68 markierten MS ist ausreichend für in vivo Anwendungen. Y-90 markierte Albumin-MS sind radiolytisch instabil und werden in vivo relativ rasch abgebaut. Sie sind deshalb kein Alternative zu den Re-188 markierten MS, die wir regelmäßig zur i.a. Therapie verwenden [1]. Dementsprechend ist auch eine Lu-177 Markierung dieser biologisch abbaubaren Partikeln nicht sinnvoll.

Literatur/References:
1] Wunderlich, G., Drews, A., Kotzerke, J. A kit for labelling of Re-188 HSA Mikrosphären for therapeutic use in nuclear medicine. Appl Radiat Isot 62 (2005) 915-918
  • Poster
    48. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 21.-24.04.2010, Leipzig, D
  • Abstract in refereed journal
    Nuklearmedizin 49(2010)2, A77

Publ.-Id: 13982 - Permalink


Modification of GaAs by Mn ion implantation towards semiconductor spintronic thin films
Bürger, D.; Zhou, S.; Pandey, M.; Grenzer, J.; Roshchupkina, O.; Anwand, W.; Reuther, H.; Gottschalch, V.; Helm, M.; Schmidt, H.;
Ferromagnetic semiconductors with high Curie temperatures and large coercivity are very promising materials for spintronic applications. An approach to fabricate ferromagnetic GaMnAs is Mn ion implantation into GaAs followed by pulsed laser annealing (PLA) [1]. Magnetic Mn ions which occupy the Ga sublattice sites form acceptor centers and pro-vide free holes for the mediation of the parallel align-ment of the magnetic moments of the Mn ions. For a strong ferromagnetic interaction, activation of the Mn acceptor dopants over their thermodynamic equilib-rium solubility is necessary. Long time, rapid thermal, and also flash lamp annealing processes take too long to realize a large enough free hole concentration by activation of Mn acceptor dopants. From a thermody-namical point of view, the PLA process is beside the more expensive LT-MBE process the best route to fabricate oversaturated ferromagnetic GaMnAs.
We investigated the influence of the implanted Mn concentration and PLA conditions on the structural and magnetic properties of GaMnAs thin films. We per-formed heatflow calculations to visualize the fast tem-peratue quenching during the PLA process [2]. Using SQUID magnetometry, we reveal a strong decrease of the saturation magnetization with increasing number of laser pulses during PLA (Fig. 1). However, the crystal-line quality is improved after several laser pulses. This has been verified by RBS (Fig. 2) and XRD measure-ments. The decrease of saturation magnetization after several laser pulses may be caused by the continuous Mn cluster formation during each PLA cycle.
[1] M. A. Scarpulla. et al. APL 82 (2003) 1251
[2] D. Bürger et al. PRB 81 115202 (2010)
  • Poster
    Ion Beam Workshop, 29.-31.03.2010, Dresden-Rossendorf, Deutschland

Publ.-Id: 13981 - Permalink


Thermodynamical limits of diluted magnetic semiconductors
Bürger, D.; Seeger, M.; Zhou, S.; Helm, M.; Schmidt, H.;
The incorporation of transition metals dopants in semiconductors over their solubility limit is the main challenge for the fabrication of diluted ferromagnetic semiconductors. Dietl et al. [1] calculated the Curie temperatures for various semiconductors doped with 5 at% Mn. A lot of experimental effort was focused on the fabrication of diluted magnetic semiconductors. Unfortunately, such metastable alloys try to reach their thermodynamical equilibrium by the diffusion of the incorporated dopants. The equilibrium state at room temperature for semiconductors with a low solubility of magnetic dopant atoms is characterized by unwanted secondary phases. We present the results from combined random walk simulations and heatflow calculations and explain the successful fabrication of GaAs:Mn and the impossibility to produce Si:Mn. The clustering process is simulated under the assumption that neighbouring magnetic atoms stick together. This is a general approach for the growth of clusters in supersaturated materials [2]. With the knowledge of the diffusion coefficient our modelling can be used to predict the thermodynamical limit at room temperature and the producibility by pulsed laser annealing of diluted magnetic semiconductors.
[1] T. Dietl, H. Ohno, F. Matsukura, J. Cibert, and D. Ferrand, Science 287, 1019 (2000)
[2] P. Meakin, Fractals, scaling and growth far from equilibrium (Cambridge University Press, 1998)
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2010, 21.-26.03.2010, Regensburg, Deutschland

Publ.-Id: 13980 - Permalink


Experimental study of the N-14(p, gamma)O-15 reaction at high and low energies
Marta, M.;
The 14N(p,gamma)15O reaction controls the rate of the hydrogen burning CNO cycle. The solar CNO neutrino flux which may be detected e.g. in Borexino and SNO+ can in principle be used to measure the carbon and nitrogen abundance at the center of the Sun, thus addressing the "solar abundance problem". However this requires more precise nuclear data. Updated results from the experimental study performed at the LUNA facility (Gran Sasso National Laboratories, Italy) in the energy range E_p = 0.36 - 0.4 MeV and from the high-current FZD Tandetron (Dresden) in the range E_p = 0.6 - 2.0 MeV are presented.
Keywords: Nuclear astrophysics; CNO cycle; TiN solid target; Tandetron; LUNA; Clover detector
  • Lecture (Conference)
    15th Workshop on Nuclear Astrophysics, 22.-27.03.2010, Schlöß Ringberg, Tegernsee, Deutschland
  • Lecture (Conference)
    International School of Nuclear Physics (32nd Course), 16.-24.09.2010, Erice (Sicily), Italy
  • Progress in Particle and Nuclear Physics 66(2011)2, 303-308
    DOI: 10.1016/j.ppnp.2011.01.025

Publ.-Id: 13978 - Permalink


Updated 14N(p,gamma)15O data from LUNA
Marta, M.; Bemmerer, D.; Caciolli, A.; Bonetti, R.; Broggini, C.; Confortola, F.; Corvisiero, P.; Costantini, H.; Elekes, Z.; Formicola, A.; Fulop, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyurky, G.; Imbriani, G.; Junker, M.; Lemut, A.; Limata, B.; Mazzocchi, C.; Menegazzo, R.; Prati, P.; Roca, V.; Rolfs, C.; Alvarez, C. R.; Somorjai, E.; Straniero, O.; Strieder, F.; Terrasi, F.; Trautvetter, H. P.;
The 14N(p,gamma)15O reaction controls the rate of the hydrogen burning CNO cycle. By detecting solar CNO neutrinos (e.g. in Borexino, SNO+) one can in principle measure directly the carbon and nitrogen abundance at the center of the Sun. However this requires more precise nuclear data. Updated experimental results on capture to various excited states (as well as to the ground state) in 15O are shown, together with improved branching ratios obtained for the E_p = 278 keV resonance.
Keywords: Nuclear astrophysics; LUNA; CNO cycle; Clover detector; TiN solid target
  • Lecture (Conference)
    Frühjahrstagung des DPG - Fachverbands Hadronen und Kerne, 15.-19.03.2010, Bonn, Deutschland

Publ.-Id: 13977 - Permalink


A possible accelerator laboratory in the Dresden Felsenkeller
Zuber, K.; Bemmerer, D.; Szücs, T.;
The field of underground accelerator physics to study rare nuclear reaction events has greatly expanded over the last decade. Consequently, there is an increasing need to put ion accelerators in underground laboratories, making use of overlying rock to suppress cosmic-ray induced background. Here we show data from a feasibility study on such a laboratory in the Dresden Felsenkeller.
  • Poster
    Astroteilchenphysik in Deutschland: Status und Perspektiven, 25.-26.02.2010, Zeuthen, Deutschland
  • Poster
    74. Jahrestagung der DPG und DPG Frühjahrstagung der Fachverbände 2010, 15.-19.03.2010, Bonn, Deutschland
  • Poster
    Nuclei in the Cosmos XI, 18.-23.07.2010, Heidelberg, Deutschland

Publ.-Id: 13976 - Permalink


An actively vetoed Clover Gamma-detector for nuclear astrophysics at LUNA
Szücs, T.; Bemmerer, D.; Broggini, C.; Caciolli, A.; Confortola, F.; Corvisiero, P.; Elekes, Z.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Lemut, A.; Marta, M.; Mazzocchi, C.; Menegazzo, R.; Prati, P.; Roca, V.; Rolfs, C.; Rossi Alvarez, C.; Somorjai, E.; Straniero, O.; Strieder, F.; Terrasi, F.; Trautvetter, H. P.;
An escape-suppressed, composite high-purity germanium detector of the Clover type has been installed at the Laboratory for Underground Nuclear Astrophysics (LUNA) facility, deep underground in the Gran Sasso Laboratory, Italy. The laboratory gamma-ray background of the Clover detector has been studied underground at LUNA and, for comparison, also in an overground laboratory. Spectra have been recorded both for the single segments and for the virtual detector formed by online addition of all four segments. The effect of the escape-suppression shield has been studied as well. Despite their generally higher intrinsic background, escape-suppressed detectors are found to be well suited for underground nuclear astrophysics studies. As an example for the advantage of using a composite detector deep underground, the weak ground state branching of the Ep = 223 keV resonance in the 24Mg(p,gamma)25Al reaction is determined with improved precision.

Publ.-Id: 13975 - Permalink


MRPC prototypes for NeuLAND tested using the single electron mode of ELBE/Dresden
Yakorev, D.; Aumann, T.; Bemmerer, D.; Boretzky, K.; Caesar, C.; Ciobanu, M.; Elekes, Z.; Elvers, M.; Hehner, J.; Heil, M.; Kempe, M.; Maroussov, V.; Nusair, O.; Reifarth, R.; Simon, H.; Stach, D.; Wagner, A.; Zilges, A.; Zuber, K.;
The NeuLAND detector at the R$^3$B experiment at the future FAIR facility in Darmstadt aims to detect fast neutrons (0.2-1.0\,GeV) with high time and spatial resolutions ($\sigma_{\rm t}$$<$100\,ps, $\sigma_{\rm x,y,z}$$<$1\,cm). The detector will consist of about 60 subsequent MRPC stacks containing a 4\,mm thick anode made of iron converter material, with an additional 4\,mm of converter material between two stacks. The secondary charged particles stemming from hadronic interactions of the high energetic neutrons in the converter will be detected in the MRPC's.

Prototypes for the NeuLAND detector have been built at FZD and GSI and then studied using the 32\,MeV pulsed electron beam at the superconducting electron accelerator ELBE in Dresden, Germany. Owing to the new, single-electron per bunch mode of operation, a rapid validation of the design criteria ($\geq$90\% efficiency for minimum ionizing particles, $\sigma$ $\leq$ 100\,ps time resolution) was possible.

Tested properties of the prototypes include glass thickness, spacing of the central anode, and a comparison of single-ended and differential readout. Tested frontend electronics schemes include FOPI (single-ended), PADI-based (both single-ended and differential mode tested), and ALICE (differential). --- Supported by BMBF (06DR9058I) and GSI FuE.
  • Lecture (Conference)
    74. Jahrestagung der DPG und DPG Frühjahrstagung der Fachverbände 2010, 15.-19.03.2010, Bonn, Deutschland

Publ.-Id: 13974 - Permalink


Experiment zur ^{14}N(p,gamma)^{15}O--Reaktion bei 0.6-2.0\,MeV
Bemmerer, D.; Beyer, R.; Broggini, C.; Caciolli, A.; Erhard, M.; Fülöp, Z.; Grosse, E.; Gyürky, G.; Hannaske, R.; Junghans, A. R.; Marta, M.; Menegazzo, R.; Nair, C.; Schwengner, R.; Szücs, T.; Trompler, E.; Wagner, A.; Yakorev, D.;
Die Rate des Bethe-Weizsäcker-Zyklus des Wasserstoffbrennens wird von der langsamsten Reaktion, ^{14}N(p,gamma)^{15}O, bestimmt. Diese Reaktion ist kürzlich u.a. bei LUNA im Energiebereich unterhalb 0.5\,MeV gründlich neu untersucht worden. Allerdings spielen auch höherenergetische Daten eine Rolle bei der Extrapolation des Wirkungsquerschnitts zu extrem niedrigen, unmessbaren Energien. Die Reaktion wurde jetzt am FZD-Tandetron im Energiebereich von 0.6-2.0\,MeV neu untersucht. --- Unterstützt von der Herbert-Quandt-Stiftung (Stipendium f\"ur T.S.) und der Europäischen Union (FP6 AIM RITA 025646).
  • Lecture (Conference)
    74. Jahrestagung der DPG und DPG Frühjahrstagung der Fachverbände 2010, 15.-19.03.2010, Bonn, Deutschland

Publ.-Id: 13973 - Permalink


NeuLAND: MRPC-based time-of-flight detector for 1 GeV neutrons
Bemmerer, D.; Elekes, Z.; Kempe, M.; Stach, D.; Wagner, A.; Yakorev, D.; Aumann, T.; Boretzky, K.; Caesar, C.; Ciobanu, M.; Hehner, J.; Heil, M.; Nusair, O.; Reifarth, R.; Simon, H.; Rossi, D.; Kratz, J. V.; Elvers, M.; Maroussov, V.; Zilges, A.;
The NeuLAND detector at the R$^3$B experiment at the future FAIR facility in Darmstadt aims to detect fast neutrons (0.2-1.0\,GeV) with high time and spatial resolutions ($\sigma_{\rm t}$$<$100\,ps, $\sigma_{\rm x,y,z}$$<$1\,cm). The detector will consist of about 60 subsequent MRPC stacks containing a 4\,mm thick anode made of iron converter material, with an additional 4\,mm of converter material between two stacks. The secondary charged particles stemming from hadronic interactions of the high energetic neutrons in the converter will be detected in the MRPC's.

As part of the ongoing development effort, a number of prototypes for this detector have been developed and built at GSI, FZD, and SINP. By testing some prototypes from GSI and FZD in experiments with picosecond electrons at ELBE (Dresden, Germany) and with 175 MeV quasi-monochromatic neutrons at TSL (Uppsala, Sweden) it was shown that the working principle is sound.
  • Lecture (Conference)
    X. Workshop on Resistive Plate Chambers and Related Detectors, 09.-12.02.2010, Darmstadt, Deutschland

Publ.-Id: 13972 - Permalink


Nuclear Physics Underground
Bemmerer, D.;
Precisely known nuclear cross sections are an essential ingredient for the modeling of nuclear processes in our Sun, in stars, and in the Big Bang. Uncertainties due to theoretical extrapolations can be avoided if experimental data are available directly at astrophysically relevant energies. Since such energies are typically far below the Coulomb barrier, this entails cross section measurements in the picobarn range.

The Laboratory for Underground Nuclear Astrophysics (LUNA) inside the Gran Sasso mountain in Italy takes up this challenge by combining accelerator-based experiments with low-background measurement techniques. Using this approach, in recent years several reactions relevant to hydrogen burning have been studied, e.g. $^3$He($\alpha$,$\gamma$)$^7$Be and $^{14}$N(p,$\gamma$)$^{15}$O. The implications of the data range from an independent lower limit on the age of the universe to a precise solar thermometer.

Based on this progress, currently there are efforts in several countries to construct new underground accelerators. The exciting science that can be probed with these new facilities will be highlighted.
  • Invited lecture (Conferences)
    VIII Latin American Symposium on Nuclear Physics and Applications, 15.-19.12.2009, Santiago, Chile
  • Contribution to proceedings
    VIII Latin American Symposium on Nuclear Physics and Applications, 15.-19.12.2009, Santiago, Chile
    AIP conference proceedings 1265: VIII Latin American Symposium on Nuclear Physics and Applications, College Park, Maryland: American Institute of Physics, 121-128
  • Lecture (Conference)
    Seminar Nukleare Astrophysik, 11.01.2010, Berlin, Deutschland

Publ.-Id: 13971 - Permalink


Determination of redox processes in biofilms from acidic waters
Krawczyk-Bärsch, E.;
First studies have been carried out in stalactite-like biofilms from the uranium mine Königstein (Germany), where the mining activities had been stopped in 1990 and the uranium mine has been partially flooded for remediation. In the acidic, sulphate-rich waters with high concentration of heavy metals and radionuclides (uranium) as contaminants, biofilms are formed and occur as gelatinous filaments, and as stalactite-like snotites. The analyses of the bacterial diversity of these biofilms showed a dominance of Ferrovum myxofaciens, an acidophilic, autotrophic, iron oxidizing bacteria, which belongs to the Betaproteobacteria. Ferrous iron is oxidized strongly catalyzed by Fe(II)-oxidizing bacteria with the consequence of producing oxidizing conditions within the biofilm with high oxygen concentration. Fiber-optic oxgyen microprofiles, carried out in these snotites are in a good agreement with electro-chemical measurements. The oxygen concentration is decreasing slowly from the edge versus center of the snotite biofilm. Electrochemical redox potential micoprofilings were carried out in these snottite-biofilms by a miniaturized platinum redox electrode with a tip diameter of 10 µm, too. In the bulk solution a redox potential of 728 mV +- 9.5 mV was measured in comparison to an increased redox potential of 834.5 mV +- 10.21 mV within the snottite-biofilm. We guess that the different geochemical conditions are due to the oxidation of ferrous iron catalyzed by Fe(II) oxidizing bacteria and that they will have an influence on the uranium speciations. A pH-Eh diagram for the U-S-O-H-C system at 15 °C was constructed using the geochemical speciation code “Geochemist´s Workbench” Version 8.0.8 / ACT2 Version 8.0.8 and the most recent NEA database for Uranyl Silicates and solid Uranates (Guillaumont et al., 2003), supplemented with solubility data for Uranophane (Nguyen et al., 1992) and CaU2O7.3H2O(s) (Altmaier et al., 2006) and the analytical data of the bulk water for the calculation of the field stability boundaries of different uranium species. The plotting of the measured pH and Eh values into this diagram showed that the theoretical stability fields of U species are defined in areas characterized by higher pH or lower Eh. The measured values indicate that aqueous Uranium(VI) Sulfate Complexations were formed in the biofilm as well as in the bulk solution. Only the changing of the local conditions (e.g. closure of the underground galleries) will lead to substantial changes and the formation of solid uranium(IV) species.
Keywords: Biofilm, uranium, redox potential, sensor measurements
  • Lecture (Conference)
    2nd Annual Workshop of ReCosy, 16.-19.03.2010, Larnaca, Cyprus

Publ.-Id: 13970 - Permalink


Electrochemical and fiber-optic oxygen sensor measurements in uranium contaminated biofilms - a collaboration with UPPC
Krawczyk-Bärsch, E.; Arnold, T.; Steinbrück, D.; Kumke, M.;
To compare the applicability of an electrochemical and a laser-based fiber-optical microsensor for oxygen determination in biofilm samples, microprofiling measurements in uranium free biofilms and in biofilms exposed to ecologically relevant uranium concentration were performed. For our studies we used a commercial available Clark-type microelectrode and a custom fiber-optic instrument, which was optimized for tip probes < 10 µm (optodes) by use of a diode laser and the so-called two frequency phase modulation technique, to mask interfering background fluorescence.
The data obtained from both microsensor methods in uranium free and uranium contaminated biofilms were in good agreement. Fiber-optic and electrochemical microsensor measurements showed high concentrations of oxygen over the total thickness of the uranium free biofilms. In contrast, biofilms exposed to uranium revealed a much lower oxygen concentration in the upper layers of the biofilm. At a biofilm depth of approximately 750 µm no oxygen was detectable at all.
Keywords: Electrochemical microsensor, fiber-optic sensor, biofilms, uranium
  • Lecture (Conference)
    2nd Annual Workshop of ReCosy, 16.-19.03.2010, Larnaca, Cyprus

Publ.-Id: 13969 - Permalink


Characterization of Xe ion-induced rippled structures on Si (001) in the medium ion energy range
Hanisch, A.; Biermanns, A.; Grenzer, J.; Pietsch, U.;
Ion-beam eroded self-organized nanostructures on semiconductors offer new ways for the fabrication of high density memory and optoelectronic devices. It is known that wavelength and amplitude of noble gas ion-induced rippled structures tune with the ion energy and the fluence depending on the energy range, ion type and substrate. The linear theory by Makeev [1] predicts a linear dependence of the ion energy on the wavelength for low temperatures. For Ar+ and Xe+ it was observed by different groups [2] that the wavelength grows with increasing fluence after being constant up to an onset fluence and before saturation. In this coarsening regime power-law or exponential behavior of the wavelength with the fluence was monitored. So far, investigations for Xe ions on silicon surfaces mainly concentrated on energies below 1keV. We found a linear dependence of both the ion energy and the fluence on the wavelength and amplitude of rippled structures over a wide range of the Xe+ ion energy between 5 and 70keV. Moreover, we estimated the ratio of wavelength to amplitude to be constant meaning a shape stability when a threshold fluence of 2x1017cm−2 was exceeded.
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2010, 22.-26.03.2010, Regensburg, Deutschland

Publ.-Id: 13968 - Permalink


Ion-beam synthesis of InSb nanocrystals within the buried SiO2 layer of silicon-on-insulator structure
Tyschenko, I. E.; Cherkov, A. G.; Voelskow, M.; Popov, V. P.;
A strong decrease of the carrier mobility of the nanometer thick silicon films imposes limitation on the application of SOI structures in the current silicon planar CMOS technology. The formation of heterostructures-on-insulator is a way to increase carrier mobility in the nanometer scale layers.
Keywords: SOI, InSb
  • Poster
    IIT 2010, 01.-07.06.2010, Kyoto, Japan

Publ.-Id: 13967 - Permalink


Doping of germanium by ion implantation and flash lamp annealing
Wündisch, C.; Posselt, M.; Schmidt, B.; Heera, V.; Mücklich, A.; Skorupa, W.; Clarysse, T.; Simoen, E.; Hortenbach, H.;
In the past the lack of stable native germanium oxide for surface passivation and gate dielectrics as well as the inability to epitaxially grow sufficiently thick defect-free germanium layers on silicon hindered the integration of germanium into the mainstream Si-based technology. Recent developments, such as high-k dielectrics and germanium-on-insulator substrates have made germanium a promising candidate for future high mobility devices. Therefore electrical doping of germanium by ion implantation and subsequent annealing has drawn a renewed interest. Investigations on the formation of ultra shallow junctions by ion beam processing have shown that p+-doping using B yields junctions that meet the requirements for the 22 nm technology node, whereas the formation of n+-junctions by P or As is complicated by the high diffusivity and the low solubility of the dopants. Recently, the concentration-dependent diffusion of n-dopants like P, As and Sb has been explored, and it has been found that doubly negatively charged vacancies are the mobile species responsible for the migration of the dopant atoms. The application of conventional rapid thermal annealing (RTA) with durations of some seconds and temperatures above about 500 °C leads to the activation of the n-dopants but their fast concentration-dependent diffusion can generally not be prevented. On the other hand it has been shown that both the diffusion and the activation of the dopants does not depend significantly on the implantation damage, i.e. using the defect engineering schemes known from Si technology seems not to be promising. Therefore, in order to control junction depth and dopant activation ultra-short annealing by flash lamps or lasers are currently under investigation.
The present work deals with the application of millisecond flash lamp annealing (FLA) to samples containing an implanted surface layer of about 100 nm thickness. P or As ions were implanted at an energy of 30 or 90 keV, respectively, and a fluence of 3x1015 cm-2. The investigations are focused on solid phase epitaxial recrystallization, dopant redistribution and dopant activation. The dependence of these effects on the heat transfer to the sample during FLA as well as on pre-amorphization and pre-annealing treatment is discussed. The results are compared to typical data achievable by RTA. Different characterization methods were employed. Channeling Rutherford backscattering spectrometry and cross-sectional transmission electron microscopy (XTEM) were used to monitor the recrystallization of the amorphous layers formed during implantation. The depth distributions of P and As were measured by secondary ion mass spectrometry. In order to determine the sheet resistance variable probe spacing and micro four point probe measurements were utilized. Selected samples were studied by XTEM to search for precipitates and end-of-range defects. While in RTA the concentration dependent dopant diffusion hinders the formation of ultra-shallow n+ layers, FLA does not cause any diffusion. The maximum activation obtained by FLA is about 6x1019 and 2x1019 cm-3 for P and As, respectively. This is about 3-4 times higher than under typical RTA conditions. However, the activation and the sheet resistance achieved by FLA do not yet fulfill the ITRS requirements for the 22 nm technology node. Possible mechanisms responsible for dopant deactivation are discussed.
Keywords: germanium, electrical doping, annealing
  • Lecture (Conference)
    Workshop Ionenstrahlphysik, 29.-31.03.2010, Dresden, Germany

Publ.-Id: 13966 - Permalink


Novel Functionalised Nanoparticles for Application in the Imaging of Cancer
Stephan, H.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    DAAD Alumni Meeting ”Tackling the future” , 26.-28.03.2010, Sydney, Australia

Publ.-Id: 13965 - Permalink


Tumor imaging using 64Cu-labeled peptides
Stephan, H.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Seminar, Bio21 Institute, School of Chemistry, University of Melbourne , 25.03.2010, Melbourne, Australia

Publ.-Id: 13964 - Permalink


Is there a real need to develop new chelating systems for radioisotopes?
Stephan, H.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Seminar, School of Chemistry, Monash University , 22.03.2010, Melbourne, Australia

Publ.-Id: 13963 - Permalink


Induction of atherogenic changes in vascular endothelial cells by radiation: role of the receptor for advanced glycation endproducts
Pietzsch, J.;
kein Abstract verfügbar
  • Poster
    Inflammation 2010, 27.-30.01.2010, Luxembourg, Luxembourg
  • Contribution to proceedings
    Inflammation 2010, 27.-30.01.2010, Luxembourg, Luxembourg
    Inflammatory cell signaling mechanisms as therapeutic targets. (Ed. Diederich M). Fondation de Recherche Cancer et Sang, Luxembourg 2010, 114

Publ.-Id: 13962 - Permalink


Influence of novel selective cyclooxygenase-2 (COX-2) inhibitors on low density lipoprotein oxidation
Pietzsch, J.; Pietzsch, F.-J.; Laube, M.; Bergmann, R.; Wuest, F.; Steinbach, J.; Kniess, T.;
kein Abstract verfügbar
  • Poster
    Inflammation 2010, 27.-30.01.2010, Luxembourg, Luxembourg
  • Contribution to proceedings
    Inflammation 2010, 27.-30.01.2010, Luxembourg, Luxembourg
    Inflammatory cell signaling mechanisms as therapeutic targets (Ed. Diederich M). Fondation de Recherche Cancer et Sang, Luxembourg 2010, 210

Publ.-Id: 13961 - Permalink


Magnetic Properties of the quasi-2D S=1/2 Heisenberg antiferromagnet [Cu(pyz)2(HF2)]PF6
Ozerov, M.; Cizmár, E.; Zvyagin, S. A.; Beyer, R.; Uhlarz, M.; Skourski, Y.; Manson, J. L.; Schlueter, J. A.; Wosnitza, J.;
We report on ESR, magnetization, and specific-heat studies of [Cu(pyz)2(HF2)]PF6 single crystals, identified as a quasi-twodimensional spin-1/2 Heisenberg antiferromagnet. Our measurements revealed Jinter/Jintrainter,Jintra, J are the interplane, intraplane and mean exchange interactions, respectively, and A is the anisotropy constant. It is argued that the magnetic properties of this material are strongly affected by two-dimensional spin fluctuations, despite of the onset of 3D long-range magnetic ordering at TN ≈ 4.4 K. The temperature-field phase diagram and ESR magnetic excitation spectrum in the 3D ordered phase of [Cu(pyz)2(HF2)]PF6 will be discussed in detail.
  • Poster
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2010, 22.-26.03.2010, Regensburg, Deutschland

Publ.-Id: 13960 - Permalink


Chiral symmetry, di-electrons and charm
Kämpfer, B.; Hilger, T.; Schade, H.; Schulze, R.; Wolf, G.;
We survey some prospects of identifying furhter in-medium modifications of hadrons in a strongly interacting medium with respect to ongoing experiment series of the HADES Collaboration and planned experiments of the CBM Collaboration at FAIR. Di-electrons, strange and charm mesons are considered and their potential for signalling imprints of chiral restoration is highlighted.
  • Contribution to proceedings
    XLVIII International Winter Meeting on Nuclear Physics in Memorian of Ileana Iori, 25.-29.01.2010, Bormio, Italy
    PoS(BORMIO2010)045

Publ.-Id: 13959 - Permalink


Optical conductivity of LuNi2B2C in the terahertz range
Fischer, T.; Pronin, A. V.; Wosnitza, J.; Niemeier, T.; Holzapfel, B.;
Using a backward-wave-oscillator-based setup in a Mach-Zehnder interferometer arrangement, we have measured the temperature and frequency-dependent transmission and phase-shift spectra of LuNi2B2C films on MgO substrates in the range 200 GHz - 1.4 THz. From the measured spectra, we have directly calculated the complex optical conductivity. We observe a clear signature of the superconducting energy gap in the spectra. In the talk, a comparison of the experimentally obtained spectra with theoretical predictions for a multi-band superconductor will be given.
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2010, 22.-26.03.2010, Regensburg, Deutschland

Publ.-Id: 13958 - Permalink


ESR Studies of the Quantum Spin Dimer System Ba3Cr2O8
Kamenskyi, D.; Wosnitza, J.; Zvyagin, S. A.; Krzystek, J.; Aczel, A. A.; Dabkowska, H. A.; Luke, G. M.;
Ba3Cr2O8 is a system of three-dimensionally coupled dimers, exhibiting a field-induced phase transition from a quantum-disordered to a long-range antiferromagnetically ordered state at Hc1 = 12.5 T. We report tunable-frequency electron spin resonance (ESR) studies of Ba3Cr2O8 single crystals performed in a frequency range between 50 and 700 GHz in fields up to 25 T (applied along the c axis). Two gaps in the magnetic excitation spectrum, Δ1 = 564 GHz and Δ2 = 400 GHz, were observed directly, confirming the spin-singlet ground state of Ba3Cr2O8 below Hc1. The observation of singlet-triplet ESR transitions, which are normally forbidden in spin-1/2 dimer systems by selection rules, indicates the break-down of the axial symmetry in this compound. Details of the ESR excitation spectrum of Ba3Cr2O8 across different regions of its phase diagram will be discussed.
  • Poster
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2010, 22.-26.03.2010, Regensburg, Deutschland

Publ.-Id: 13957 - Permalink


Annual Report 2009 - Institute of Radiochemistry
Bernhard, G.; Foerstendorf, H.; Richter, A.; Viehweger, K.; (Editors)
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-530 2010

Downloads:

Publ.-Id: 13956 - Permalink


Schlussbericht zum BMBF-Vorhaben "Entwicklung und Erprobung neuer Instrumente zur Bildung von Verwertung- und Transfernetzen" NanoFoto - Neue Wege zur verwertungsorientierten Netzwerkbildung in der Nanobiotechnologie
Raff, J.;
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-529 2010

Downloads:

Publ.-Id: 13955 - Permalink


Effect of Gallium Doping on Superconductivity in Germanium
Skrotzki, R.; Herrmannsdörfer, T.; Heera, V.; Ignatchik, O.; Uhlarz, M.; Mücklich, A.; Posselt, M.; Reuther, H.; Schmidt, B.; Heinig, K.-H.; Skorupa, W.; Voelskow, M.; Wündisch, C.; Fiedler, J.; Helm, M.; Wosnitza, J.;
We report recent discoveries of superconductivity in Ga-doped germanium fabricated by ion implantation and subsequent flash-lamp or oven annealing. Tuning the preparation parameters allows for varying both charge-carrier and Ga concentration in the resulting roughly 100 nm thin nano- or single-crystalline layers. Transport measurements on systematically prepared samples reveal that besides a needed charge-carrier concentration of more than 0.4 atom%, superconductivity occurs to be sensitive on the implanted Ga content which may also be attributed to a change in the phonon properties. Onset transition temperatures up to 1.4 K have been found for almost 10 atom% Ga. Further, we observe in-plane critical fields exceeding 1 T and being close to the Pauli-Clogston limit. An exceptionally low Cooper-pair density of around 1015 cm−3 turns out the extreme type-II character of superconductivity. Finally, our work adds to our previous report [1] and may help to understand superconductivity in doped elemental semiconductors in general.
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2010, 22.-26.03.2010, Regensburg, Deutschland

Publ.-Id: 13954 - Permalink


Magnetic field effects in electrochemical reactions
Mutschke, G.; Koschichow, D.; Peipmann, R.; Bund, A.; Fröhlich, J.; Weier, T.; Tschulik, K.; Uhlemann, M.;
Today's available strong magnets allow to study distinct magnetic effects in various electrochemical systems. Lorentz forces and also magnetic gradient forces can be utilized to tailor convection and mass transfer in electrolytic cells, thereby influencing for example the morphology and the structure of the electrodeposits. The presentation will give an overview on recent results of numerical simulations and experimental findings in lab-scale electrochemical systems and will discuss potential applications. Whereas Lorentz forces are often known to enhance mass transfer, new results show that the convection pattern found in simple geometries can already be quite complex. A deeper understanding is required for improved applications. Recently, also magnetic gradient forces gained attention, e.g. for their potential in preparing micro-structured deposits. A detailed discussion of recent results will give further insight. Finally, new investigations of cyclic operation modes or time-dependent magnetic fields are presented which allow for a broad range of new phenomena.
Keywords: magnetoelectrochemistry, Lorentz force
  • Invited lecture (Conferences)
    Pacifichem 2010, 15.-20.12.2010, Honolulu, Hawaii, USA

Publ.-Id: 13953 - Permalink


Neue (UO2)2+-Komplexe von Bis(2-hydroxyaryl)imin-Liganden: Synthese, Struktur und Extraktionseigenschaften
Gloe, K.; Tanh Jeazet, H. B.; Doert, T.; Gloe, K.; Geipel, G.; Bernhard, G.;
Die Koordinationschemie von Uran(VI) hat in den letzten Jahren vielfältiges Interesse gefunden. Ursachen dafür sind sowohl dessen Bedeutung im Rahmen der Kernenergiegewinnung als auch Probleme bei der Aufarbeitung sowie Lagerung von verbrauchten Kernbrennstoffen. Weitere Fragestellungen beziehen sich auf die Umweltrelevanz von U(VI) als Folge seiner natürlichen Verbreitung sowie bergbaulicher Altlasten. Schließlich werden auch potentielle Anwendungsoptionen von spezifischen Komplexverbindungen des Urans diskutiert.
Wir haben einige Imin-Liganden synthetisiert und drei neue Komplexverbindungen mit UO2(NO3)2 strukturell charakterisiert. Zum Vergleich wurden auch die strukturanalogen Aminderivate in die Untersuchungen einbezogen. Extraktionsexperimente mit den genannten Liganden zeigen differenzierte Extraktionseigenschaften gegenüber U(VI) mit einer ausgeprägten Selektivität gegenüber Eu(III).
Keywords: Extraction study, Imine-ligand, radioactive waste, uranium
  • Lecture (Conference)
    Jahrestreffen des Fachausschusses Extraktion., 18.-19.03.2010, Kaiserslautern, Germany

Publ.-Id: 13952 - Permalink


Quantitative Kelvin probe force microscopy imaging on locally doped semiconductors
Baumgart, C.; Müller, A.-D.; Müller, F.; Helm, M.; Schmidt, H.;
Kelvin probe force microscopy (KPFM) is used for the nanoscale characterization of semiconductors. Quantitative dopant profiling by means of KPFM measurements is successfully shown on a conventional static random access memory (SRAM) cell and on cross-sectionally prepared Si epilayer structures by applying a recently introduced new explanation of the measured KPFM signal [1]. The presented KPFM model is also used to explain observed large conductivity differences in different Mn implanted and pulsed laser annealed Ge samples by revealing a strong variation of the Fermi level position on the µm scale in dependence on the annealing conditions after Mn implantation [2].
In addition, it will be shown that due to surface state formation and charge trapping in a thin native oxide layer the Kelvin bias probed above differently doped regions strongly depends on the measurement frequency [3]. Therefore, KPFM measurements have to be performed at frequencies high enough so that the electrical properties of the locally doped semiconductor and not of the oxide layer are probed.

[1] C. Baumgart, M. Helm, H. Schmidt, Phys. Rev. B 80, 085305 (2009).
[2] S. Zhou, D. Bürger, C. Baumgart, W. Skorupa, C. Timm, P. Oesterlin, M. Helm, H. Schmidt, submitted.
[3] F. Müller and A.-D. Müller, J. Vac. Sci. Techn. B 27, 969 (2009).
  • Lecture (Conference)
    International Conference on Functional Nanocoatings 2010, 28.-31.03.2010, Dresden, Deutschland

Publ.-Id: 13951 - Permalink


Self-organization during the growth of phase-separated nanostructured thin films
Abrasonis, G.;
Control over the morphology and spatial correlations at the nanoscale is one of the major challenge of the nowadays nanoscience and nanotechnology. Bottom-up approaches to nanostructured material synthesis are based on self-organization processes to precisely define ordered nanostructures on a large scale. Self-organization occurs via the interplay between two factors - an external constraint acting on internal system processes. During the thin film growth this is translated into the interplay between thermodynamic driving forces and kinetic constraints. In this talk I will summarize the recent research activities of our group on the phase separation during the growth of carbontransition metal thin films. Different processes can be ’switched off/on’ by external control of the experimental parameters such as temperature, substrate type, matrix/dispersed phase chemical affinity or incoming particle energy. This results in a large variety of lateral or vertical composition modulations, such as encapsulated nanoparticles, high aspect ratio nanocolumns or self-organized layered 3D nanoparticle arrays. Such self-organization process is versatile as different carbontransition metal systems show this effect. The observed tendencies will be discussed on the basis of the interplay of thermal and energetic ion induced phenomena.
  • Invited lecture (Conferences)
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2010, 22.-26.03.2010, Regensburg, Germany

Publ.-Id: 13950 - Permalink


Actinide Redox Speciation and Structure Analysis in Aqueous and Nonaqueous Solutions
Hennig, C.;
Actinide redox chemistry plays a crucial role in nuclear technology like fuel reprocessing and nuclear waste disposal aspects including predicting of actinide mobility in the environment. Hydrolysis and complex formation of the early actinides are strongly related with their redox behavior in aqueous and nonaqueous solutions. We are interested in understanding the complexation of actinide compounds under controlled redox conditions in presence of inorganic oxo ligands and organic ligands with carboxylic groups.
This study is mainly focused on the use of EXAFS spectroscopy in combination with other supporting methods. The information from EXAFS spectroscopy is restricted to a pair distribution function providing coordination numbers and distances of the next neighbors. Two pathways were used to relate this information to the spatial arrangement of the ligands: (i) EXAFS was combined with DFT calculations which introduce constraints of molecular characteristics [1], and (ii) individual solution species were preserved in crystal structures and determined with single crystal diffraction. EXAFS was used subsequently to quantify differences or identify agreement between the coordination of complex structures in solution and solid state [2-4]. EXAFS is furthermore not very sensitive to differentiate between individual solution species, especially in not a single sample. This problem was solved in the following manner: (i) combination of EXAFS with other more species sensitive techniques, e.g. like UV-Vis spectroscopy [5] and (ii) by using sample series with broad variation of species distribution and subsequent application of statistical analysis techniques to separate the scattering contribution of individual solution species [6]. Finally, we investigated the correlation between the formal redox potential and the stability range of solution species [7].

[1] Hennig et al. The sulfate coordination of Np(IV), Np(V) and Np(VI) in aqueous solution. Inorg. Chem. 48 (2009) 5350-5360.
[2] Hennig et al. Comparative investigation of the solution species [U(CO3)5]6 and the crystal structure of Na6[U(CO3)5]•12H2O. Dalton Trans. 39 (2010) 3744–3750.
[3] Takao et al. First hexanuclear UIV and ThIV formate complexes – structure and stability range in solution. Eur. J. Inorg. Chem. (2009) 4771-4775.
[4] Hennig et al. Coordination of a uranium(IV) monomer in aqueous solution and in solid state. Inorg. Chem. 47 (2008) 1634-1638.
[5] Hennig et al. The relationship of monodentate and bidentate coordinated uranium(VI) sulfate in aqueous solution. Radiochim. Acta 96 (2008) 607-611.
[6] Hennig et al. Species distribution and coordination of uranyl chloro complexes in acetonitrile. Inorg. Chem. 47 (2008) 2987-2993.
[7] Takao et al. Complex formation and molecular structure of neptunyl(VI) and –(V) acetates. Inorg. Chem. 48 (2009) 8803-8810.
Keywords: Actinides, redox chemistry, EXAFS, UV-Vis, DFT, XRD
  • Contribution to proceedings
    APS users meeting 2010, 03.-05.05.2010, Argonne/Illinois, USA
    APS users meeting 2010 - Celebrating 20 Years of Groundbreaking Science, 48-48
  • Invited lecture (Conferences)
    APS users Meeting, 03.-05.05.2010, Argonne, USA

Publ.-Id: 13949 - Permalink


Prediction of polydisperse steam bubble condensation in sub-cooled water using the Inhomogeneous MUSIG model
Lifante, C.; Frank, T.; Burns, A. D.; Lucas, D.; Krepper, E.;
The aim of this paper is to present the validation of a new methodology implemented in ANSYS CFX (ANSYS, 2009), that extends the standard capabilities of the inhomogeneous MUltiple-SIze Group model (MUSIG) by additionally accounting for bubble size changes due to heat and mass transfer. Bubble condensation plays an important role in sub-cooled boiling or steam injection into pools among many other applications of interest in the Nuclear Reactor Safety (NRS) area and other engineering areas. Since the mass transfer rate between phases is proportional to the interfacial area density, a polydisperse modelling approach considering different bubble sizes is of main importance, because an accurate prediction of the bubble diameter distribution is required.
The standard MUSIG approach is an inhomogeneous one with respect to bubble velocities, which combines the size classes into different so-called velocity groups to precisely capture the different behaviour of the bubbles depending on their size. In the framework of collaboration between ANSYS and the Forschungszentrum Dresden-Rossendorf (FZD) an extension of the MUSIG model was developed, which allows to take into account the effect of mass transfer due to evaporation and condensation on the bubble size distribution changes in addition to breakup and coalescence effects.
After the successful verification of the model, the next step was the validation of the new developed model against experimental data. For this purpose an experiment was chosen, which was investigated in detail at the TOPFLOW test facility at FZD. It consists of a steam bubble condensation case at 2MPa pressure in 3.9K sub-cooled water at a large diameter (DN200) vertical pipe. Sub-cooled water flows into the 195.3 mm wide and 8 m height pipe, were steam is injected at z=0.0 m and is recondensing. The experimental results are published in (Lucas, et al., 2007). Using a wire-mesh sensor technique the main characteristics of the two-phase flow were measured, i.e. radial steam volume fraction distribution and bubble
diameter distribution at different heights and cross-sections.
ANSYS CFX 12.0 was used for the numerical prediction. A 60 degrees pipe sector was modelled in order to save computational time, discretized into a mesh containing about 260.000 elements refined towards the pipe wall and towards the location of the steam injection nozzles. Interfacial forces due to drag, lift, turbulent dispersion and wall lubrication force were considered. The numerical results were compared to the experimental data. The agreement is highly satisfactory, proving the capability of the new MUSIG model extension to accurately predict such complex two-phase flow.
Keywords: CFD, water/steam flow, MUSIG, polydisperse flow, phase change
  • Contribution to proceedings
    7th International Conference on Multiphase Flow, ICMF 2010, 30.05.-04.06.2010, Tampa, FL, USA
    paper 5.6.4
  • Lecture (Conference)
    7th International Conference on Multiphase Flow, ICMF 2010, 30.05.-04.06.2010, Tampa, FL, USA

Publ.-Id: 13948 - Permalink


Analysis of developing gas/liquid two-phase flows
Tselishcheva, E. A.; Podowski, M. Z.; Antal, S. P.; Post Guillen, D.; Beyer, M.; Lucas, D.;
The objective of this work has been to study the mechanisms governing flow and phase distributions in developing gas/liquid two phase flows in general, and the evolution of different size bubbles in an adiabatic vertical pipe in particular. Flow regimes from bubbly to churn-turbulent have been accounted for. The main emphasis of the work has been on the modeling of various interfacial forces between the dispersed bubbles and the continuous liquid, as well as of bubble/bubble interactions (coalescence and breakup).
The proposed modeling concept uses a complete set of transport equations for each field, such as the continuous liquid and dispersed bubble fields. The overall model has been implemented in a state-of-the-art computational multiphase fluid dynamics code, NPHASE–CMFD. This three-dimensional four-field model, including the continuous liquid field and three dispersed gas fields representing bubbles of different sizes, has been carefully tested for numerical convergence and accuracy, and then validated against the TOPFLOW experimental results.
The NPHASE-CMFD simulations were aimed at demonstrating the capability of the proposed modeling concepts to predict the evolution of bubble concentration from channel inlet to near-equilibrium (fully-developed) conditions downstream. Along with several interfacial closure laws, the effect of elevation on air density has also been included in the model.
Keywords: gas/liquid two phas flow, NPHASE-CMFD, interfacial forces, bubble/bubble interaction, coalescence, breakup, TOPFLOW
  • Contribution to proceedings
    7th International Conference on Multiphase Flow, ICMF 2010, 30.05.-04.06.2010, Tampa, USA
    Analysis of developing gas/liquid two-phase flows
  • Lecture (Conference)
    7th International Conference on Multiphase Flow, ICMF 2010, 30.05.-04.06.2010, Tampa, USA

Publ.-Id: 13947 - Permalink


A simple design for a continuous magnetically guided positron beam - and - news from the EPOS project
Krause-Rehberg, R.; Jungmann, M.; Werlich, B.; Pohl, A.; Anwand, W.; Brauer, G.; Butterling, M.; Krille, A.; Wagner, A.; Kosev, K.; Cowan, T.;
In the first part of the contribution, a rather simple design of a conventional, magnetically guided, continuous positron beam will be presented. The moderator is a tungsten mesh and the energy selection is realized using a bent tube. The sample is on ground potential. Further details will be presented during the talk.
In the second part of the talk, the recent progress of the EPOS project at the Research Center Dresden-Rossendorf will be demonstrated. EPOS consists of a pulsed monoenergetic positron beam (MePS), a conventional lifetime/Doppler spectrometer (CoPS), and a setup for gamma-induced positron annihilation spectroscopy (GiPS). While CoPS and GiPS systems are available for user operation, the MePS system is still under construction. First positrons were moderated and fed into the positron lab. At the moment, the chopper/buncher/accelerator system is under construction.
Keywords: positron annihilation, continuous magnetically guided positron beam, pulsed monoenergetic positron beam
  • Invited lecture (Conferences)
    International Workshop on Advanced Positron Beam Technology for Material Science, 15.-18.03.2010, Algiers, Algeria

Publ.-Id: 13946 - Permalink


Positron study of ion-cutting process in GaN
Guittoum, A.; Moutanabbir, O.; Jungmann, M.; Butterling, M.; Krause-Rehberg, R.; Anwand, W.; Egger, W.; Sperr, P.;
We report on the nature of vacancy complexes and voids involved in H ion-induced splitting of free standing fs-GaN. The fs-GaN wafers were subjected to room temperature implantation with 50 keV H ions at a fluence of 2x1017 H cm-2. After implantation, the wafers were annealed at different temperatures ranging from 100 to 600 °C. Variable energy Doppler broadening spectroscopy (VEDBS) was used in order to probe open-volume defects and their thermoevolution. Pulsed low energy positron lifetime spectroscopy (PLEPLS) was employed to qualitively characterize H ion-induced vacancy complexes and to observe their subtle changes during the thermally activated splitting of GaN thin layer. The decomposition of the lifetime spectra of as-implanted and annealed samples up to a temperature of 450 °C resulted in the detection of two vacancy defects: divacancies (260-282 ps) and vacancy clusters (470-650 ps). With increasing temperature, we have noted in addition the existence of other kind of vacancy-type defects, namely, monovacancies (220-236 ps) and a long lifetime which is attributed to positronium. From the values of positronium lifetime equal to 1 ns, 2.2 ns and 3.8 ns, it was possible to estimate the corresponding wall spacing according to the Tao-Eldrup model to be 0.2 nm to 0.4 nm. The fact that positron annihilation spectroscopy can give information about the wall spacing in GaN, leads us to say that this technique is able to predict the phenomenon of splitting in wide band gap semiconductors.
Keywords: ion-cutting, GaN, positron annihilation spectroscopy
  • Invited lecture (Conferences)
    International Workshop on Advanced Positron Beam Technology for Material Science - APSB 2010, 15.-18.03.2010, Algiers, Algeria

Publ.-Id: 13945 - Permalink


Electromagnetic induction in non-uniform domains
Giesecke, A.; Nore, C.; Luddens, F.; Stefani, F.; Leorat, J.; Guermond, J.-L.; Gerbeth, G.;
Kinematic simulations of the induction equation are carried out for different setups suitable for the von-Karman-Sodium (VKS) dynamo experiment. Material properties of the flow driving impellers are considered by means of high conducting and high permeability disks that are present in a cylindrical volume filled with a conducting fluid. Two entirely different numerical codes are mutually validated by showing quantitative agreement on Ohmic decay and kinematic dynamo problems using various configurations and physical parameters. Field geometry and growth rates are strongly modified by the material properties of the disks even if the high permeability/high conductivity material is localized within a quite thin region. In contrast the influence of external boundary conditions remains small.

Utilizing a VKS like mean fluid flow and high permeability disks yields a reduction of the critical magnetic Reynolds number for the onset of dynamo action of the simplest non-axisymmetric field mode. However this decrease is not sufficient to become relevant in the VKS experiment. Furthermore, the reduction of Rm_c is essentially influenced by tiny changes in the flow configuration so that the result is not very robust against small modifications of setup and properties of turbulence.
Keywords: Magnetohydrodynamics, Ohmic decay, kinematic Dynamo, Permeability, VKS dynamo

Publ.-Id: 13944 - Permalink


Velocity fields under impinging jets with gas entrainment
Danciu, D.-V.; Zidouni Kendil, F.; Mishra, A.; Schmidtke, M.; Lucas, D.; Hampel, U.;
Particle Image Velocimetry (PIV) is a powerful measurement technique, suitable for the study of complex flow fields encountered in single- or two-phase flow phenomena. Air entrainment is a widely studied phenomenon, which is encountered in multiple industrial applications, as well as in nature. Results from the successful application of PIV to both impinging region and recirculation zone are presented. Both instantaneous and time-averaged flow fields were obtained. The turbulent kinetic energy is estimated from the averaged velocity fields in the recirculation zone. Simulations of the phenomenon are performed with ANSYS-CFX. The turbulence was modelled using the k-epsilon model. Experimental results were compared with the simulation and showed good agreement.
Keywords: gas entrainment, particle image velocimetry, liquid velocity fields, simulation
  • Lecture (Conference)
    7th International Conference on Multiphase Flow ICMF 2010, 30.05.-04.06.2010, Tampa, USA
  • Contribution to proceedings
    7th International Conference on Multiphase Flow, ICMF 2010, 30.05-04.06.2010, Tampa,USA, 30.05.-04.06.2010, Tampa, USA
    International Conference on Multiphase Flow

Publ.-Id: 13943 - Permalink


The 9th International Conference on Research in High Magnetic Fields in Retrospective View
Wosnitza, J.; Herrmannsdörfer, T.; Wolff-Fabris, F.;
es hat kein Abstract vorgelegen
  • Journal of Low Temperature Physics 159(2010), 1-2

Publ.-Id: 13942 - Permalink


Superconducting Phase Diagram of Rh17S15
Uhlarz, M.; Ignatchik, O.; Wosnitza, J.; Naren, H. R.; Thamizhavel, A.; Ramakrishnan, S.;
We report on measurements of the magnetization up to 7 T, of the specific heat and electrical resistivity in fields up to 14 T, and of the magnetic susceptibility in fields up to 20 T of a polycrystalline sample of Rh17S15. Our data allow us to complement the superconducting phase diagram. The existence of narrow 4 d-band states (and thus of strong electronic correlations that seem not to provide magnetic correlations) is supported by the moderately high electronic contribution to the specific heat of about 107 mJ/molK2, favoring the existence of a strong superconducting interaction. This fact, and the remarkably high upper critical field (exceeding the simple Pauli limit by a factor of two), give evidence of the uncommon nature of the superconductivity in Rh17S15.
  • Journal of Low Temperature Physics 159(2010), 176-179

Publ.-Id: 13941 - Permalink


Magneto-Acoustic Faraday Effect in Tb3Ga5O12
Sytcheva, A.; Löw, U.; Yasin, S.; Wosnitza, J.; Zherlitsyn, S.; Goto, T.; Wyder, P.; Lüthi, B.;
The transverse acoustic wave propagating along the [100] axis of the cubic paramagnet Tb3Ga5O12 (TGG) exhibits amplitude oscillations as a function of magnetic field applied in the direction of propagation. This magneto-acoustic Faraday effect shows a linear frequency dependence contrary to theoretical expectation which demands a quadratic frequency dependence. The c44 mode demonstrates also a strong softening of 6% up to 19 T, the magnetic field where an energy level of the CEF triplet branch starts to cross the quasi-doublet branch. This softening has the same origin, the magneto-elastic coupling, as the anomalies in the temperature dependence of the elastic constants and the magneto-acoustic Faraday effect.
  • Journal of Low Temperature Physics 159(2010), 126-129

Publ.-Id: 13940 - Permalink


Magnetoacoustics of the Low-Dimensional Quantum Antiferromagnet Cs2CuCl4 with Spin Frustration
Sytcheva, A.; Chiatti, O.; Wosnitza, J.; Zherlitsyn, S.; Zvyagin, A. A.; Coldea, R.; Tylczynski, Z.;
We report on results of sound-velocity and sound-attenuation measurements in the triangular-lattice spin-1/2 antiferromagnet Cs2CuCl4 (TN = 0.6 K), in external magnetic fields up to 14 T, applied along the b axis, and at temperatures down to 300 mK. The results are analyzed with a quasi-two-dimensional hard-core boson theory based on exchange-striction coupling. There is a good qualitative agreement between theoretical and experimental results.
  • Journal of Low Temperature Physics 159(2010), 109-113

Publ.-Id: 13939 - Permalink


Microminiature Hall Probes for Applications at Pulsed Magnetic Fields up to 87 Tesla
Mironov, O. A.; Zherlitsyn, S.; Uhlarz, M.; Skourski, Y.; Palewski, T.; Wosnitza, J.;
Microminiature Hall probes (MHP) may be used as magnetic field transducers, with virtually no change of sensitivity with temperature, for applications at room and cryogenic temperatures. The probes have a nominal active sensing area from 90 × 90 μm down to 20 × 20 μm and are based on Sn-doped n-InSb/i-GaAs MBE-grown heterostructures. MHPs were intensively tested in static (up to 14 T) and pulsed magnetic fields and shown to be appropriate for various applications in the temperature range 2–300 K and in pulsed magnetic fields up to 87 T. The latest version of these probes, with overall cross-section thickness-width dimensions of 150 × 750 μm, are the smallest encapsulated Hall probes currently available and can be placed in areas not previously accessible to commercial packaged or unpackaged sensors.
  • Journal of Low Temperature Physics 159(2010), 315-318

Publ.-Id: 13938 - Permalink


Upper Critical Field Measurements up to 60 T in Arsenic Deficient LaO0.9F0.1FeAs1−δ: Pauli Limiting Behavior at High Fields vs. Improved Superconductivity at Low Fields
Fuchs, G.; Drechsler, S.-L.; Kozlova, N.; Freudenberger, J.; Bartkowiak, M.; Wosnitza, J.; Behr, G.; Nenkov, K.; Büchner, B.; Schultz, L.;
We report resistivity and upper critical field Bc2(T ) data for As-deficient LaO0.9F0.1FeAs1−δ in a wide temperature and field range up to 60 T. These disordered samples exhibit a slightly enhanced superconducting transition at Tc = 29 K and a significantly enlarged slope dBc2/dT = −5.4 T/K near Tc which contrasts with a flattening of Bc2(T ) starting near 23 K above 30 T. This flattening is interpreted as Pauli limiting behavior (PLB) with Bc2(0) ≈ 63 T. We compare our results with Bc2(T )-data reported in the literature for clean and disordered samples. Whereas clean samples show no PLB for fields below 60 to 70 T, the hitherto unexplained flattening of Bc2(T ) for applied fields H || ab observed for several disordered closely related systems is interpreted also as a manifestation of PLB. Consequences of our results are discussed in terms of disorder effects within the frame of conventional and unconventional superconductivity.
  • Journal of Low Temperature Physics 159(2010), 164-167

Publ.-Id: 13937 - Permalink


High-Field Magnetization Study of [Cu(pyz)2(HF2)]PF6: An S = 1:2 Quasi-two-dimensional Heisenberg Magnet
Cizmar, E.; Ozerov, M.; Skourski, Y.; Zvyagin, S. A.; Schlueter, J. A.; Manson, J. L.; Wosnitza, J.;
We report on pulsed-field magnetization studies of the quasi-two-dimensional spin system [Cu(pyz)2(HF2)]PF6. The magnetization saturates at BabC = 37.5 T and BcC= 33.8 T for in-plane and out-of-plane orientations of the applied magnetic field, respectively. In addition, the angular dependence of the g-factor studied by electron-spin resonance reveals orbital overlap in the ab plane suggesting a quasi-two-dimensional square-lattice network of Cu spins. It is argued that the high-field behavior is governed by the two-dimensional nature of the spin correlations due to the large anisotropy of the exchange couplings.
  • Journal of Low Temperature Physics 159(2010), 92-95

Publ.-Id: 13936 - Permalink


A High Resolution, Broad Energy Acceptance Spectrometer for Laser Wake-field Acceleration Experiments
Sears, C. M. S.; Benavides Cuevas, S.; Schramm, U.; Schmid, K.; Buck, A.; Habs, D.; Krausz, F.; Veisz, L.;
Laser wake¯eld experiments present a unique challenge in measuring the resulting electron energy properties due to the large energy range of interest, typically several 100 MeV, and the large electron beam divergence and pointing jitter >1 mrad. In many experiments the energy resolution and accuracy are limited by the convolved transverse spot size and pointing jitter of the beam. In this paper we present an electron energy spectrometer consisting of two magnets designed speci¯cally for laser wake¯eld experiments. In the primary magnet the ¯eld is produced by permanent magnets while a second electromagnet can be used for electron energies above 75 MeV. The spectrometer has an acceptance of 2.5-400 MeV (Emax=Emin > 100) with a resolution of better than 1% rms for electron energies above 25 MeV. This high resolution is achieved by refocusing electrons in the energy plane and without any post-processing image deconvolution. Finally, the spectrometer employs two complimentary detection mechanisms: 1) absolutely calibrated scintillation screens imaged by cameras outside the vacuum chamber, and 2) an array of scintillating ¯bers coupled to a low-noise CCD.
Keywords: Laser plasma electron acceleration, magnetic spectrometer, scintillating fiber array

Publ.-Id: 13935 - Permalink


Radionuclide Geomicrobiology of the Deep Biosphere
Anderson, C.; Johnsson, A.; Moll, H.; Pedersen, K.;
This review summarizes research into interactions between microorganisms and radionuclides under conditions typical of a repository for high-level radioactive waste in deep hard rock environments at a depth of approximately 500 m. The cell-radionuclide interactions of strains of Pseudomonas species (i.e., Shewanella putrefaciens and Desulfovibrio aespoeensis) with Cm, Pm, and Pu were investigated in vitro and the results were found to agree with literature data. Siderophores are capable of binding actinides strongly and need to be considered in terms of radionuclide mobility in the subsurface. Siderophores and other bioligands were found to have a generally very strong mobilizing effect on Am, Cm, Fe, Np, Pm, Pu, Th, and U. Where reduced groundwater enters an aerobic environment, such as a large open fracture or fracture zone (e.g., in tunnels), there is the possibility of rapid aerobic bacterial metabolism, microbial proliferation, biofilm development, and iron oxide formation. In these environments, the stalk-forming bacterium Gallionella may act as a scaffold for iron oxide precipitation on biological material. In situ work in the Äspö Hard Rock Laboratory tunnel indicated that the concentrations of biological iron oxides, lanthanides, and actinides correlated positively with Gallionella biomass, a finding that compares well to literature data. In deep oligotrophic subsurface granitic rock environments, fracture biofilms reach a threshold of approximately 2-5 x 106 cells/cm2. The cells in these biofilms are spatially distinct and are surrounded by an extracellular polysaccharide matrix that constitutes up to 60% of the total organic carbon. Calcium-rich amorphous masses are associated with this base layer of cells and organic exudates. In situ, these biofilms have been found to influence the adsorption and immobilization of Am, Np, Pm, Th, and U. This review demonstrates that microorganisms can influence, and sometimes even control, the migration behavior of radionuclides in deep geological environments typical of future sites for radioactive waste repositories.
Keywords: Radionuclides, Geomicrobiology, Deep biosphere

Publ.-Id: 13934 - Permalink


Some nuclear reactor safety related aspects of plunging jets
Krepper, E.; Weiss, F.-P.; Alt, S.; Kratzsch, A.; Renger, S.; Kästner, W.;
Plunging jets play an important role in nuclear reactor safety research. In the present paper the case of the strainer clogging issue is considered. Entrained air caused by a plunging jet has an influence of the liquid flow field and on the fibre transport in the sump. In the paper the amount of entrained air is given as an inlet boundary condition according to correlations in the literature and confirmed by own experiments. The influence of entrained air on the fibre deposition pattern at the bottom of a tank and on the mixing procedure for the case of temperature differences between jet and tank water are investigated by CFD calculations and compared to experiments.
The presented work is part of a joint research project performed in cooperation between the University of Applied Science Zittau/Görlitz and Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow in Zittau and the development of CFD models for its simulation in Rossendorf (Krepper et al. 2008).
Keywords: fibres, experiments, cfd, multiphase flow
  • Contribution to proceedings
    18th International Conference on Nuclear Engineering, ICONE18, 17.-21.05.2010, Xi'an, China
  • Lecture (Conference)
    18th International Conference on Nuclear Engineering, ICONE18, 17.-21.05.2010, Xi’an, China

Publ.-Id: 13933 - Permalink


Quantum Transport and Cyclotron Resonance Study of Ge/SiGe Quantum Wells in High Magnetic Fields
Miura, N.; Kozlova, N. V.; Dörr, K.; Freudenberger, J.; Schultz, L.; Drachenko, O.; Sawano, K.; Shiraki, Y.;
Shubnikov-de Haas oscillation and cyclotron resonance were studied for high mobility p-type Ge channels in strained Ge/Si1-x Ge (x) quantum wells, using pulsed high magnetic fields up to 50 T. Fine quantum oscillations were observed in rho (xx) . Reflecting the complex Landau level structure in the nearly degenerate valence bands, the Fourier transform of the oscillatory spectra consists of several peaks. Cyclotron resonance was measured at photon energies between 10 and 17 meV. Two well-defined resonance peaks were observed in two samples with different x, resulting in different strains. A large non-parabolicity and large strain dependence of the effective masses were observed.
Keywords: Ge/SiGe quantum well; Magneto-spectroscopy

Publ.-Id: 13932 - Permalink


Cyclotron Resonance of Extremely Conductive 2D Holes in High Ge Content Strained Heterostructures
Mironov, O. A.; Goiran, M.; Galibert, J.; Kozlov, D. V.; Ikonnikov, A. V.; Spirin, K. E.; Gavrilenko, V. I.; Isella, G.; Kummer, M.; von Känel, H.; Drachenko, O.; Helm, M.; Wosnitza, J.; Morris, R. J. H.; Leadley, D. R.;
Cyclotron resonance has been observed in steady and pulsed magnetic fields from high conductivity holes in Ge quantum wells. The resonance positions, splittings and linewidths are compared to calculations of the hole Landau levels.
Keywords: Cyclotron resonance, Ge, SiGe, Landau Levels

Publ.-Id: 13931 - Permalink


Treasures as seen under proton irradiation
Neelmeijer, C.;
Silicate materials such as glass, porcelain and ceramics, but also geological findings are characterized by their chemical composition. Corresponding fingerprints of unique pieces - e.g. precious objects of art - have to be studied stringently in a non-destructive manner. Elements along the whole periodic system are of analytical interest. These requirements are met by ion beam analysis (IBA) using protons of 4 MeV energy extracted from vacuum into atmospheric pressure. Atoms of the object of investigation, struck by protons, emit characteristic γ-radiation due to nuclear reactions as well as X-rays via proton-electron interactions. Simultaneous detection of PIGE (Particle Induced Gamma-ray Emission) and PIXE (Particle Induced X-ray Emission) signals allows determination of all chemical constituents. PIGE measures the concentration of the main element Si, consequently the SiO2 content. Moreover, PIGE gives the concentrations of accompanying light elements like Li, B, Na, Mg and Al and their natural oxides; also F can be examined.
Maximum information depths in glass are in the order of 40 µm. Hence, the PIGE results represent the silicate material bulk. PIXE provides concentrations of the elements heavier than Al (Z > 13). Maximum PIXE information depths in glass are only 10 µm, which is due to much higher attenuation of X-rays (E~keV) compared to that of γ-rays (E~MeV). Therefore, the PIXE results stand for the bulk material only if the object surface was not attacked by strong deterioration. PIGE-PIXE analysis of silicate materials must be executed in an interactive manner in order to account for radiation absorption effects. Protons reflected from atoms situated in depth regions near the material surface, i.e. Rutherford Backscattering Spectrometry (RBS), inform of environmental degradation. Thus, IBA is best-suited to calculate both the state of preservation as well as the possible danger of progressive deterioration regarding cultural heritage, especially which made from glass [1].
As is known, K-Ca-silica glass gets decomposed by leaching when being exposed to humid surroundings, even under air conditioning in museum collections. Both, protective storage and preventive conservation have become one of the primary tasks in museum science. The performance of IBA is figuring out glass objects of endangered composition as long as indications of alteration are still not visible. Exhibits sui generis dated from baroque era and treasured inside the museum of applied arts in Dresden were already exposed to the proton beam in air. Several exhibits show visually opacity, some of them a network of fine cracks. The final evaluation of measured data is in the offing. Composition analysis of single obsidian pieces has been a topic of international interest. For their characterization questions have concentrated on fingerprints regarding elements heavier than Fe, being enclosed with low concentrations.
For the bulk materials of interest IBA detection limits are in the order of 5 - 300 µg/g, thus falling for light elements Z < 22 (Ti) below that of X-ray fluorescence spectrometry.

Reference: [1] M. Mäder, C. Neelmeijer, Nucl. Instr. and Meth. B 226 (2004) 110 - 118
Keywords: analysis, non-destructive, ion beam analysis, PIGE, PIXE, RBS, art, preventive conservation, obsidian, detection limits
  • Lecture (Conference)
    Analytica2010, 23.-25.03.2010, München, Germany

Publ.-Id: 13930 - Permalink


Countercurrent gas-liquid flow in a hot leg under reflux cooling - numerical calculations for steam-water tests at FZD
Kinoshita, I.; Murase, M.; Utanohara, Y.; Lucas, D.; Vallée, C.; Tomiyama, A.;
Numerical calculations using FLUENT6.3.26 were conducted for steam-water CCFL tests using the 1/3rd scale rectangular channel simulating a PWR hot leg at FZD, and the results were compared with the FZD data.
Keywords: PWR, reflux cooling, hot leg, countercurrent gas-liquid flow, numerical calculations
  • Contribution to proceedings
    Annual meeting of the Atomic Energy Society of Japan, 26.-28.03.2010, Ibaraki, Japan, 237

Publ.-Id: 13929 - Permalink


Countercurrent gas-liquid flow in a hot leg under reflux cooling - numerical calculations for air-water tests at FZD
Murase, M.; Kinoshita, I.; Utanohara, Y.; Lucas, D.; Vallée, C.; Tomiyama, A.;
Numerical calculations using FLUENT6.3.26 were conducted for air-water CCFL tests using the 1/3rd scale rectangular channel simulating a PWR hot leg at FZD, and the results were compared with CCFL characteristics in circular tubes.
Keywords: PWR, reflux cooling, hot leg, countercurrent gas-liquid flow, numerical calculations
  • Contribution to proceedings
    Annual meeting of the Atomic Energy Society of Japan, 26.-28.03.2010, Ibaraki, Japan, 236

Publ.-Id: 13928 - Permalink


High field cyclotron resonance spectroscopy using quantum cascade lasers
Drachenko, O.;
Author reviews practical aspects of application of quantum cascade lasers (QCL) to high field laser magneto-spectroscopy of semiconductors. The universal QCL based experimental set-up, covering wide spectral region from 5 up to 120mm is presented. The performance of the setup is illustrated with cyclotron resonance measurements of InGaAs/GaAs and InAs/AlSb quantum wells.
Keywords: cyclotron resonance, high magnetic field, semiconductors, effective mass, quantum cascade laser
  • Invited lecture (Conferences)
    The XIV Nanophysics and Nanoelectronics Symposium, 15.-19.03.2010, Nizhny Novgorod, Russia

Publ.-Id: 13927 - Permalink


The Transformation Pathways of Mo6S2I8 Nanowires into Morphology-Selective MoS2 Nanostructures
Virsek, M.; Krause, M.; Kolitsch, A.; Mrzel, A.; Iskra, I.; Skapin, S. D.; Remskar, M.;
Nanomaterials prepared by the sulfurization of Mo6S2I8 nanowires and the time and temperature dependence of the transformation process are investigated by high-resolution transmission electron microscopy, X-ray powder diffraction, and wavelength-dependent Raman spectroscopy. Depending on the temperature, coaxial MoS2 nanotubes or MoS2 “mama”-tubes are formed after 2 h of sulfurization. Using a few minutes of sulfurization time, core-shell nanowires composed of well-ordered MoS2 layers covering a Mo6S2I8 core are formed, proving an outside-to-inside transformation process. The crystallinity of the three MoS2 nanostructures increases with increasing transformation temperature, i.e., in the sequence from MoS2/Mo6S2I8 core-shell structures via coaxial MoS2 tubes to the MoS2 “mama”-tubes. The analysis indicates a different nature of the defects in the MoS2-based nanomaterials, originating from the sulfurization of the Mo6S2I8 than in the conventional MoS2 platelike crystals. A correlation between the Raman spectroscopic parameters and the defect density in MoS2 is identified.

Publ.-Id: 13926 - Permalink


Helium irradiation study on zircon
Nasdala, L.; Grambole, D.; Götze, J.; Kempe, U.; Váczi, T.;
Synthetic ZrSiO4 and (mildly to strongly radiation-damaged) natural zircon samples were irradiated with 8.8 MeV 4He2+ ions (fluences in the range 1 x 1013 – 5 x 1016 ions/cm²). For comparison, an additional irradiation experiment was done with 30 MeV 16O6+ ions (fluence 1 x 1015 ions/cm²). The light-ion irradiation resulted in the generation of new (synthetic ZrSiO4) or additional (mildly to strongly metamict natural samples) damage, respectively. The maximum extent of the damage is observed in a shallow depth range approximately 32–33 µm (8.8 MeV He) and ≤ 12 µm (30 MeV O) below the sample surface, respectively, i.e., near the end of the ion trajectories. These depth values, and the observed damage distribution, correspond well to defect distribution patters as predicted by Monte Carlo simulations. The irradiation damage is recognised from the notable broadening of Raman-active vibrational modes, lowered interference colours (i.e., decreased birefringence), and changes in the optical activity (i.e., luminescence emission). At very low damage levels, a broad-band yellow emission centre is generated whereas at elevated damage levels, this centre becomes re-suppressed and samples experience a general decrease of their emission intensity. Most remarkably, there is no indication of any structural recovery process in pre-damaged natural zircon as induced by the light-ion irradiation, which questions the relevance of alpha-assisted annealing of radiation damage in natural zircon.
Keywords: Zircon, Ion irradiation, Radiation damage, Raman spectroscopy, Luminescence

Publ.-Id: 13923 - Permalink


Visualization and holdup measurement of viscous oil-water dispersed pipe flow by capacitance wire-mesh sensor
Da Silva, M. J.; Hampel, U.; Rodriguez, I. H.; H. Rodriguez, O. M.;
Experiments were performed in a test facility at NETeF (Thermal-Fluids Engineering Laboratory) of the Engineering School of São Carlos. The facility consists basically of a horizontal glass pipe of 26 mm of inner diameter and 12 m length. Mineral oil (860 kg/m3 density and 100 mPa∙s viscosity) and tap water stored in separated tanks are circulated under controlled conditions through the test pipe. The flow rates of each liquid are individually controlled and measured. After passing the horizontal test section, the mixture flows to a coalescent-plate separator tank. The liquids once separated are returned to their respective storage tanks by gravity. A wire-mesh sensor with 8 x 8 wire configuration was installed close to end of the horizontal pipe at 10.3 m from the entrance. To assemble the wire-mesh sensor in the test pipe, a flange of transparent Perspex was manufactured which allows for optical observations (Fig 1a). A high-speed camera (Optronis, Camrecord 600) was applied to monitor the flow patterns and investigate the influence of wire-mesh sensor in the flow.
Experiments were performed at oil superficial velocity between 0.2 m/s to 1 m/s and water superficial velocity between 1 m/s to 3 m/s. The recording speed was 2000 fps for the high-speed camera and 500 fps for the wire-mesh sensor, whereby data acquisition of both systems was synchronized by a common trigger signal. Figure 1b and 1c show exemplary images of the flow obtained by the both imaging devices. Note that the high-speed camera depicts a lateral view of the flow, while the wire-mesh sensor images show holdup distributions over the cross section of the pipe. From the two-dimensional holdup distribution measured by the wire-mesh sensor we have further determined liquid holdup integrated over different domains thus obtaining time and/or spatially averaged holdup values, e.g. radial profiles or mean holdup. Furthermore, for comparison purposes of holdup measurements, the quick-closing valves (QCV) technique was employed. Good agreement was found between QCV and WMS techniques. In the full paper, a complete description of the measurements will be presented along with a discussion of the accuracy in the measurements.
Keywords: wire mesh sensor, oil-water two-phase flow
  • Contribution to proceedings
    6th World Congress On Industrial Process Tomography (WCIPT6), 06.-09.09.2010, Bejing, China
    Proceedings of the 6th World Congress On Industrial Process Tomography, 1334-1440

Publ.-Id: 13922 - Permalink


Secondary Radiation during 7Li Irradiation of a PMMA Phantom
Kormoll, T.; Fiedler, F.; Müller, A.; Enghardt, W.;
no abstract available
Keywords: prompt gamma emission, in-vivo dosimetry
  • Contribution to external collection
    in: GSI Scientific Report, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung, 2010

Publ.-Id: 13921 - Permalink


Fluorine-18 labeling of phosphopeptides: a potential approach for the evaluation of phosphopeptide metabolism in vivo.
Richter, S.; Bergmann, R.; Pietzsch, J.; Ramenda, T.; Steinbach, J.; Wuest, F.;
Phosphopeptides are very useful reagents to study signal transduction pathways related with cellular protein phosphorylation/dephosphorylation. Phosphopeptides have also been identified as important drug candidates to modulate intracellular signaling mechanisms through targeting phosphotyrosine, phosphoserine, or phosphothreonine residue-binding protein domains. In this report, we describe the development of a convenient method for the mild and sufficient radiolabeling of phosphopeptides with the short-lived positron emitter fluorine-18 (18F) to allow radiopharmacological studies on phosphopeptide metabolism in vivo by means of positron emission tomography (PET). Radiolabeling was accomplished via conjugation of the N-terminus of polo-box domain (PBD)-binding phosphopeptide H-Met-Gln-Ser-pThr-Pro-Leu-OH with the bifunctional labeling agent N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) in reproducible isolated radiochemical yields of 25-28%. Radiopharmacological evaluation in vitro and in vivo of radiolabeled phosphopeptide [18F]FB-Met-Gln-Ser-pThr-Pro-Leu-OH [18F]-3 and its non-phosphorylated analog [18F]FB-Met-Gln-Ser-Thr-Pro-Leu-OH [18F]-4 involved metabolic stability, cell uptake studies, and small animal PET experiments. Radiolabeled phosphopeptide [18F]-3 showed a remarkable high metabolic stability in vivo compared to the corresponding non-phosphorylated peptide [18F]-4. The presented method indicates that radiolabeling of phosphopeptides with [18F]SFB is a promising approach for studying phosphopeptide metabolism in vivo.
Keywords: phosphopeptides; fluorine-18; positron emission tomography (PET)

Publ.-Id: 13920 - Permalink


Formation of uranium(IV)-silica colloids at near-neutral pH
Dreissig, I.; Weiss, S.; Hennig, C.; Bernhard, G.; Zänker, H.;
Evidence is provided by photon correlation spectroscopy, ultrafiltration and ultracentrifugation that uranium(IV) can form silicate-containing colloids of a size of 620 nm. A concentration of up to 103 M of colloid-borne U(IV) was observed. The particles are generated in near-neutral to slightly alkaline solutions containing background chemicals of geogenic nature (carbonate, silicate, sodium ions). They remain stable in aqueous suspension over years. Electrostatic repulsion due to a negative zeta potential in the near-neutral to alkaline pH range caused by the silicate stabilizes the U(IV) colloids. The isoelectric point of the nanoparticles is shifted toward lower pH values by the silicate. The mechanism of the colloidal stabilization can be regarded as “sequestration” by silicate, a phenomenon well known from heavy metal ions of high ion potential such as iron(III) or manganese(III,IV), but never reported for uranium(IV) so far. Extended X-ray absorption fine structure (EXAFS) spectroscopy showed that U–O–Si bonds, which increasingly replace the U–O–U bonds of the amorphous uranium(IV) xyhydroxide with increasing silicate concentrations, make up the internal structure of the colloids. The next-neighbor coordination of U(IV) in the U(IV)-silica colloids is comparable with that of coffinite, USiO4. The assessment of uranium behavior in the aquatic environment should take the possible existence of U(IV)-silica colloids into consideration. Their occurrence might influence uranium migration in anoxic waters.
Keywords: colloid; uranium(IV); silicic acid; EXAFS; coffinite; carbonate; reduction

Publ.-Id: 13918 - Permalink


Monitoring of multi-phase distribution in packing columns using wire-mesh sensor
Zheng, G.; Schubert, M.; Hampel, U.; Grünewald, M.;
Absorption packing columns employing gas-liquid counter-current flow are widely used across a wide range of industries. Maldistribution of liquid phase could reduce the contact area of both phases, thus lowering column efficiency. Liquid holdup is an essential parameter that influence pressure drop and load capacity of the packing column. Traditional measurements of local liquid holdups using liquid collector strongly disturb the original conditions which make the results less reliable. In this study the local liquid holdup and their distribution was measured with the state-of-the-art technology using wire-mesh sensor installed below the packing.
Wire-mesh sensor contains 16x16 orthogonally arranged wires (up to 32x32), measuring the complex impedance at every sensing point which is related to the local permittivity over the whole cross section. Matrices which denote the local permittivity are obtained with a frequency up to 1000 frames per second. Knowing pure gas and liquid phase permittivity allows calculation of local phase fractions. Unlike ECT or ERT measurement, grid sensor excellently locates the liquid phase position and the area obstruction is lower than 1 percent.
Stochastic behavior of liquid flow at different time was found. It is shown that large scale of maldistribution near the wall was observed and most of liquid phase flows preferentially in the same zones.
The amount of liquid flowing along the column wall was characterized by analyzing liquid holdups of the annular grid points. It is shown that more than 27% of the liquid phase flows improperly and its amount varies dynamically.
Mesurements with wire-mesh sensor could be employed to correct essential parameters such as effective phase contact area, local liquid holdup and etc. Therefore, mass transfer laws suggested by Billet (1995) and hydraulic model by Mackowiak (2009) could be modified.
Keywords: grid sensor, packing column, distribution, multi-phase
  • Contribution to proceedings
    6th World Congress on Industrial Process Tomography (WCIPT6), 06.-09.09.2010, Bejing, China
    Proceedings of the 6th World Congress on Industrial Process Tomography, pp. 1473-1487

Publ.-Id: 13917 - Permalink


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