Helmholtz-Gemeinschaft
DRESDEN-concept

Mobile version: On

Publication database - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

< Seite 1 von 194 >   Gesamtzahl lt. Auswahl: 19325 Title records (100 Title records je Seite)
23785 Publications
Hypoxia-inducible factor pathway inhibition resolves tumor hypoxia and improves local tumor control after single-dose irradiation.
Helbig, L.; Koi, L.; Brüchner, K.; Gurtner, K.; Hess-Stumpp, H.; Unterschemmann, K.; Pruschy, M.; Baumann, M.; Yaromina, A.; Zips, D.
Abstract: PURPOSE:

To study the effects of BAY-84-7296, a novel orally bioavailable inhibitor of mitochondrial complex I and hypoxia-inducible factor 1 (HIF-1) activity, on hypoxia, microenvironment, and radiation response of tumors.
METHODS AND MATERIALS:

UT-SCC-5 and UT-SCC-14 human squamous cell carcinomas were transplanted subcutaneously in nude mice. When tumors reached 4 mm in diameter BAY-84-7296 (Bayer Pharma AG) or carrier was daily administered to the animals. At 7 mm tumors were either excised for Western blot and immunohistologic investigations or were irradiated with single doses. After irradiation animals were randomized to receive BAY-84-7296 maintenance or carrier. Local tumor control was evaluated 150 days after irradiation, and the dose to control 50% of tumors (TCD50) was calculated.
RESULTS:

BAY-84-7296 decreased nuclear HIF-1α expression. Daily administration of inhibitor for approximately 2 weeks resulted in a marked decrease of pimonidazole hypoxic fraction in UT-SCC-5 (0.5% vs 21%, P<.0001) and in UT-SCC-14 (0.3% vs 19%, P<.0001). This decrease was accompanied by a significant increase in fraction of perfused vessels in UT-SCC-14 but not in UT-SCC-5. Bromodeoxyuridine and Ki67 labeling indices were significantly reduced only in UT-SCC-5. No significant changes were observed in vascular area or necrosis. BAY-84-7296 before single-dose irradiation significantly decreased TCD50, with an enhancement ratio of 1.37 (95% confidence interval [CI] 1.13-1.72) in UT-SCC-5 and of 1.55 (95% CI 1.26-1.94) in UT-SCC-14. BAY-84-7296 maintenance after irradiation did not further decrease TCD50.
CONCLUSIONS:

BAY-84-7296 resulted in a marked decrease in tumor hypoxia and substantially reduced radioresistance of tumor cells with the capacity to cause a local recurrence after irradiation. The data suggest that reduction of cellular hypoxia tolerance by BAY-84-7296 may represent the primary biological mechanism underlying the observed enhancement of radiation response. Whether this mechanism contributes to the improved outcome of fractionated chemoradiation therapy warrants further investigation.
Registration No. 21634

Development of a Laser wakefield acceleration source as a secondary radiation driver
Couperus, J. P.; Jochmann, A.; Köhler, A.; Messmer, M.; Zarini, O.; Debus, A.; Hübl, A.; Widera, R.; Bussmann, M.; Sauerbrey, R.; Cowan, T.; Schramm, U.; Irman, A.
Abstract: In laser wakefield electron acceleration a high intensity ultrashort laser pulse drives plasma density waves, inducing a high accelerating field gradient (~GV/m) which can accelerate electrons to high energies within a very short distance.
For the development of secondary radiation sources, the maximization of the bunch charge is important. For this reason we investigate the beam-loading effect at the self-injected highly nonlinear regime. Beam-loading deteriorates the accelerating field structure and limits the maximum bunch charge.
Supported by intensive Particle-in-Cell code simulations run on a GPU-cluster (using the PIConGPU code), we aim on developing a stable high peak current (hundreds of kA) electron source.

Keywords: laser wakefield electron acceleration LWFA plasma PIConGPU
  • Poster
    Advanced School on Laser Applications at Accelerator, 29.09.-03.10.2014, Salamanca, Spain
Registration No. 21632

Investigation of the beam loading effect in laser wakefield acceleration
Couperus, J. P.; Jochmann, A.; Köhler, A.; Messmer, M.; Zarini, O.; Debus, A.; Hübl, A.; Widera, R.; Bussmann, M.; Sauerbrey, R.; Cowan, T.; Schramm, U.; Irman, A.
Abstract: In laser wakefield electron acceleration a high intensity ultrashort laser pulse drives plasma density waves, inducing a high accelerating field gradient (~GV/m) which can accelerate electrons to high energies within a very short distance.
For the development of secondary radiation sources, the maximization of the bunch charge is important. For this reason we investigate the beam-loading effect at the self-injected highly nonlinear regime. Beam-loading deteriorates the accelerating field structure and limits the maximum bunch charge.

Keywords: laser plasma electron acceleration LWFA wakefield gas-jet PIConGPU
  • Poster
    International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Deutschland
Registration No. 21630

Energy-Angle Characteristic of an ICS source
Jochmann, A.
Abstract: A tunable source of intense ultra-short hard X ray pulses represents a novel tool for the structural analysis of complex systems with unprecedented temporal and spatial resolution. At Helmholtz-Zentrum Dresden-Rossendorf (HZDR) we demonstrated the principle of such a light source (PHOENIX – Photon Electron collider for Narrow bandwidth Intense X-Rays) by colliding picosecond electron bunches from the ELBE linear accelerator with counter-propagating femtosecond laser pulses from the 150 TW Draco Ti:Sapphire laser system. The generated narrowband X rays are highly collimated and can be reliably adjusted by tuning the electron energy. A complete spectral characterization of this source is performed with high angular and energy resolution. These intensive studies provide predictive capability for the future high brightness hard X ray source PHOENIX and potential gamma-ray sources suited to an application.
Keywords: Laser Compton Scattering X-ray pulsed source femtosecond intense backscattering inverse
  • Lecture (Conference)
    LA3NET 3rd Topical Workshop on Novel Acceleration Techniques, 28.04.2014, Dresden, Deutschland
Registration No. 21628

Effect of a superimposed DC magnetic field on an AC induction semi-levitated molten copper droplet
Bojarevics, A.; Beinerts, T.; Grants, I.; Kaldre, I.; Sivars, A.; Gerbeth, G.; Gelfgats, J.
Abstract: While a piece of pure Copper on a ceramic substrate was inductively melted by 9 to 18 kHz AC magnetic field with axial magnetic DC field superimposed, the liquid metal stably semi-levitated in the expected “conical” free surface shape. The diameter of the liquid metal at the basis was 30 mm, the volume – more than 20 cm3. Replacing the ceramic substrate with a Glassy Carbon, which was not wetted by the molten Copper, caused instability of the semi-levitated Copper droplet. In the absence of the DC field severe chaotic instabilities of the liquid metal shape occurred, causing splashes and uncontrolled contact with crucible walls. When axial DC magnetic field with induction 0.35 T was superimposed the liquid metal droplet exhibited harmonic azimuthal wave deformation of the free surface. Higher frequencies lead to smaller characteristic wavelength. Transverse DC magnetic field direction suppressed the travelling wave deformations of the droplet shape. Stabilizing effect of the DC magnetic field during induction melting has been shown for axial, transverse and 45 degree direction magnetic field. These results experimentally demonstrate the possibilities to improve the stability of levitated metal volumes by superimposed DC magnetic field.
Keywords: -
  • Lecture (Conference)
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Lettland
  • Contribution to proceedings
    9th PAMIR conference on Fundamental and Applied MHD,, 16.-20.06.2014, Riga, Lettland
    Proceedings of the 9th PAMIR conference on Fundamental and Applied MHD, Vol 2, 125-129
Registration No. 21627

Experimental modelling using liquid metals
Gerbeth, G.; Eckert, S.
Abstract: An overview on liquid metal modelling experiments is presented for the steel casting process. Particular attention is given to the recent developments on measuring techniques for liquid metal flows, including the perspectives for measurements in real steel melts.
Keywords: -
  • Invited lecture (Conferences)
    VDEh Steel Academy Workshop „Computational Fluid Dynamics in Metallurgy“, 01.-03.12.2014, Mönchengladbach, Deutschland
Registration No. 21626

Recent results on flow measurements and magnetic control
Gerbeth, G.; Eckert, S.
Abstract: A brief summary is given on measurements in metal melts developed at HZDR. Melt velocities can be measured by local electromagnetic probes, ultrasonic Doppler velocimetry and by the Contactless Inductive Flow Tomography (CIFT). The latter is fully contactless and offers a possibility for an online monitoring of the melt flow. We report on first test measurements with CIFT at Czochralski facilities for Si growth. Regarding the details of solidification and the occurrence of inclusions, we present results on X-ray visualizations of alloy solidification. They allowed to demonstrate for metal alloys the formation of freckles driven by the mesoscopic melt convection ahead of the solidification front. For the magnetic melt control we present results of model experiments on the reduction of buoyant temperature oscillations using a rotating magnetic field. Related studies were performed for cylindrical melt volumes and a Cz-like configuration. The melt flow in the float-zone process can be efficiently influenced by a so-called magnetic two-phase stirrer. Its principle and related growth results for intermetallic compounds will be presented.
Keywords: -
  • Lecture (others)
    DGKK-Tagung, 12.-13.03.2014, Halle, Deutschland
Registration No. 21625

Towards laser wakefield acceleration with external injection at HZDR
Irman, A.
Abstract: Progress towards laser wakefield acceleration with external injection is presented.
  • Invited lecture (Conferences)
    Novel acceleration techniques ANAC2/EUCARD2 JRA meeting, 30.04.2014, HZDR, Germany
Registration No. 21624

High Resolution Energy-angle Correlation Measurement of Hard X rays from Laser Thomson Backscattering
Irman, A.; Bussmann, M. H.; Couperus, J. P.; Debus, A. D.; Jochmann, A.; Pausch, R. G.; Schlenvoigt, H. P.; Schramm, U.; Steiniger, K.; Cowan, T. E.; Kuntzsch, M.; Lehnert, U.; Sauerbrey, R.; Seipt, D.; Wagner, A.; Ledingham, K.; Stöhlker, T.; Thorn, D. B.; Trotsenko, S.
Abstract: A tunable source of intense ultra-short hard X ray pulses represents a novel tool for the structural analysis of complex systems with unprecedented temporal and spatial resolution. At Helmholtz-Zentrum Dresden-Rossendorf (HZDR) we demonstrated the principle of such a light source (PHOENIX – Photon Electron collider for Narrow bandwidth Intense X-Rays) by colliding picosecond electron bunches from the ELBE linear accelerator with counter-propagating femtosecond laser pulses from the 150 TW Draco Ti:Sapphire laser system. The generated narrowband X rays are highly collimated and can be reliably adjusted by tuning the electron energy. A complete spectral characterization of this source is performed with high angular and energy resolution. These intensive studies provide predictive capability for the future high brightness hard X ray source PHOENIX and potential gamma-ray sources suited to an application.
Keywords: Laser Compton Scattering X-ray pulsed source femtosecond intense backscattering inverse
  • Poster
    IPAC’14 - 5th International Particle Accelerator Conference, 18.06.2014, Dresden, Deutschland
Registration No. 21623

Fluid dynamics research at HZDR Dresden
Gerbeth, G.
Abstract: An overview on fluid dynamics research activities is given, including multiphase and magnetohydrodynamic flows and the related computational fluid dynamics.
Keywords: -
  • Invited lecture (Conferences)
    Shandong Universität, 11.05.2014, Jinan, China
Registration No. 21622

Laser-plasma based electron acceleration
Irman, A.
Abstract: The concept of laser-driven plasma-based electron acceleration is reviewed. This lecture will be started by description of plasmas and its characteristics then follows with electron injection and acceleration. In the end, recent progress in the field will be highlighted.
Keywords: laser wakefield acceleration
  • Invited lecture (Conferences)
    LA3NET Advanced School on Laser Applications at Accelerators, 28.09.-03.10.2014, Salamanca, Spain
Registration No. 21621

Research on crystal growth problems at Institute of Fluid Dynamics of HZDR
Gerbeth, G.
Abstract: Research activities at HZDR on the measurement and magnetic field control of melt flows in crystal growth processes are summarized. Examples are given for the tailored control by magnetic fields of Czochralski, Vertical-Gradient-Freeze as well as Float-Zone growth processes.
Keywords: -
  • Invited lecture (Conferences)
    SICC Science & Technology, Ltd., 12.05.2014, Jinan, China
Registration No. 21620

Tornado-like flows driven by magnetic body forces
Gerbeth, G.; Grants, I.; Vogt, T.; Eckert, S.
Abstract: Alternating magnetic fields produce well-defined flow-independent body forces in electrically conducting media. This property is used to construct a laboratory analogue of the Fiedler chamber with a room-temperature liquid metal as working fluid. A continuously applied rotating magnetic field (RMF) provides the source of the angular momentum. A pulse of a much stronger travelling magnetic field drives a converging flow at the metal surface, which focuses this angular momentum towards the axis of the container. The resulting vortex is studied experimentally and numerically. In a certain range of the ratio of both driving actions the axial velocity changes its direction in the vortex core, resembling the subsidence in an eye of a tropical cyclone or a large tornado. During the initial deterministic spin-up stage (T. Vogt et al., JFM 736, 2013, pp. 641) the vortex is well described by axisymmetric direct numerical simulation. Being strong enough the flow develops a funnel-shaped surface depression that enables visual observation of the vortex structure. As the RMF strength is increased the eyewall diameter grows until it breaks down to multiple vortices. A number of further observed similarities to tornado-like vortices will be discussed.
Keywords: -
  • Invited lecture (Conferences)
    APS-DFD 2014 meeting, 23.-25.11.2014, San Francisco, USA
  • Abstract in refereed journal
    Bulletin of the American Physical Society 59(2014), 20
Registration No. 21619

Correlation of electron and laser beam parameters to the spectral shape and bandwidth of laser-Thomson backscattering x-ray beams
Irman, A.; Jochmann, A.; Debus, A.; Couperus, J. P.; Trotsenko, S.; Kuntzsch, M.; Lehnert, U.; Wagner, A.; Schlenvoigt, H.-P.; Bussmann, M.; Sthöhlker, Th.; Seipt, D.; Thorn, D. B.; Ledingham, K. D.; Cowan, T.; Sauerbrey, R.; Schramm, U.
Abstract: Development of advanced x-ray sources based on laser-Thomson scattering mechanism is becoming important pushed by a strong demand for ultrashort hard x-ray pulses, which can serve as a novel tool for structural analysis of complex systems with unprecendented temporal and spatial resolution. The spectral shape and bandwidth of this x-ray beam is the result from the interplay between interacting electron and laser beam parameters. We present high resolution angle and energy resolved measurements on the x-ray photon distribution generated by colliding picosecond electron bunches from the ELBE linear accelerator with counter-propagating laser pulses from the 150 TW DRACO Ti:Sapphire laser system. The measured data and an ab-initio comparison with the 3D radiation code CLARA enable us to reveal parameter influences and correlation of both interacting beams. We conclude that in the low laser intensity interaction regime the electron angular distribution and the laser bandwidth, as in the case of ultrashort laser pulses, give a strong influence to the x-ray spectral shape and bandwidth. We also show the x-ray spectral broadening as the laser intensity increases indicating nonlinear interaction on the scattering process. Controlling these parameters is necessary for designing future Thomson x-ray sources with a specific bandwidth suited to an application.
Keywords: laser-Thomson backscattering x-ray, ELBE electron beam, ultrashort x-ray, high power laser
  • Invited lecture (Conferences)
    16th Advanced Accelerator Concepts Workshop (AAC 2014), 13.-18.07.2014, San Jose, United States
Registration No. 21618

LIMTECH A5: Liquid metal two-phase flows
Strumpf, E.; Eckert, S.; Richter, T.; Gerbeth, G.
Abstract: Measurements for rising single bubbles were performed in a cuboid benchmark experiment filled with the liquid metal GaInSn. Data was acquired by two different ultrasound techniques simultaneously, which are Ultrasound Doppler Velocimetry (UDV) and Ultrasound Transit Time Technique (UTTT). The focus was on the influence of a horizontal magnetic field on the bubble behavior.
Keywords: liquid metal, two-phase, single bubble, horizontal magnetic field, UDV, UTTT
  • Poster
    LIMTECH annual meeting 2014, 10.-11.11.2014, Ilmenau, Deutschland
Registration No. 21617

The Tayler instability at low magnetic Prandtl numbers
Stefani, F.; Barry, L.; Gundrum, T.; Kirillov, O.; Seilmayer, M.; Weber, N.; Gellert, M.; Rüdiger, G.
Abstract: The Tayler instability is a kink type instability which appears when an axial current in a cylinder crosses a certain critical value. It has been discussed as a main ingredient of the Tayler-Spruit stellar dynamo model, but may also play a role as a size-limiting factor in large-scale liquid metal batteries. We discuss several theoretical aspects and the first experimental evidence of the Tayler instability in liquid metals.
  • Lecture (Conference)
    European GdR Dynamo Meeting, 01.-04.09.2014, Cambridge, England
Registration No. 21613

The present status of the DRESDYN project
Stefani, F.
Abstract: The DRESDYN project at Helmholtz-Zentrum Dresden-Rossendorf is intended as a platform for large-scale liquid sodium experiments on dynamo action and magnetically triggered flow instabilities. We report on the progress of the building construction, and on the design status of the precession driven dynamo experiment. Special focus is laid on new theoretical and experimental results on the magnetorotational and Tayler instability, and on the consequences for the planned liquid sodium experiment for the combined study of those instabilities. Some very recent results of a small-scale spherical Couette experiment with an applied axial magnetic field are also discussed.
  • Invited lecture (Conferences)
    Grands séminaires ISTerre, 13.11.2014, Grenoble, France
Registration No. 21612

The present status of the DRESDYN project
Stefani, F.
Abstract: The DRESDYN project is new platform for a variety of liquid sodium experiments, comprising a large-scale precession driven dynamo experiment and a combined set-up for investigating different versions of the magnetorotational instability and the Tayler instability. We sketch the history of previous liquid metal experiments on cosmic magnetic field, and outline the status of preparations for the various facilities planned in the framework of DRESDYN.
  • Invited lecture (Conferences)
    MHD-Days 2014, 02.-03.12.2014, Potsdam, Germany
Registration No. 21611

The new ELBE Center for High Power Radiation Sources at HZDR: Status and Opportunities
Seidel, W.
Abstract: The ELBE user facility located at the Helmhotz-Zentrum Dresden-Rossendorf operates a superconducting electron linear accelerator , which provides short (picosecond) electron bunches with energies up to 35 MeV at a 13 MHz repetition rate. Here we discuss the basic parameters of the ELBE Center and the experimental opportunities at the facility.
  • Invited lecture (Conferences)
    Turkish-German Workshop on Particle Accelerators and Light Sources, 09.-10.07.2014, Istanbul, Turkey
Registration No. 21609

Theranostic mercury: 197(m)Hg with high specific activity for imaging and therapy
Walther, M.; Preusche, S.; Bartel, S.; Wunderlich, G.; Freudenberg, R.; Steinbach, J.; Pietzsch, H.-J.
Abstract: The no carrier added (NCA) radionuclide 197(m)Hg is accessible through proton induced nuclear reactions on gold.The decay properties of both simultaneous produced nuclea risomers 197mHg and 197Hg like convenient half life, low energy gamma radiations for imaging, Auger and conversion electrons for therapy are combined with unique chemical and physical properties of mercury and its compounds. Gold as a monoisotopic element has a natural abundance of 100% 197Au superseding expensive enrichment for the target material. Additionally, the high thermal conductivity of gold enables high beam current irradiations. For separation of target material a liquid–liquid extraction method was applied.
Keywords: 197Hg; Theranostics; Dosimetry; 177Lu; Auger and conversion electrons Registration No. 21607

Wissens- und Innovationsgemeinschaften (KIC) am Beispiel des KIC Rohstoffe - nachhaltige Erkundung, Gewinnung, Verarbeitung, Verwertung und Substitution
Dirlich, S.; Klossek, A.
Abstract: Der Vortrag erläutert anhand von drei Leitfragen (Ziele von KIC, Synergien zur nationalen Forschung und aktuelle Entwicklungen) Wissens- und Innovationsgemeinschaften im Allgemeinen und geht im Besondere auf das geplante KIC Rohstoffe ein. Mit dem KIC Rohstoffe sollen die Ziele "vom Labor in den Markt", "vom Studenten zum Unternehmer" und "von der Idee zum Produkt" auf den Rohstoffsektor übertragen werden. Dabei wird die gesamte Kette von der Erkundung bis zum Recycling berücksichtigt. Für deutsche Wissenschaftler gibt es zahlreiche Synergiemöglichkeiten angesichts eines europäischen Netzwerks aus fast 120 Partnern aus den Bereichen Forschung, Bildung und Industrie. Das KIC beschäftigt sich insbesondere mit der Rohstoffverfügbarkeit in Europa, der Substitution kritischer Rohstoffe und der Nachhaltigkeit in der gesamten Kette der Rohstoffindustrie.
Keywords: raw materials, resources supply, innovation, knowledge, KIC
  • Invited lecture (Conferences)
    11. Fona-Forum, 29.09.2014, Berlin, Deutschland
Registration No. 21606

NeuLAND time of flight detector for 200-1000 MeV neutrons read out by fast photosensors
Bemmerer, D.
Abstract: A new setup for kinematically complete reaction experiments for beams of radioactive nuclei far from the valley of stability is under construction at FAIR Darmstadt, Germany. NeuLAND, a highly efficient (>90%) neutron time of flight detector made of fast plastic scintillators is included in the setup. In order to reach proper resolution in the reconstructed energy spectrum, a time resolution of sigma < 150 ps is required. Using the ELBE picosecond electron beam as a time reference, it is currently being studied whether semiconductor-based photosensors (SiPMs) can be used for the readout of the NeuLAND scintillator bars.
  • Lecture (Conference)
    WINS 2014 Workshop on Elastic and Inelastic Neutron Scattering, 03.-05.12.2014, Dresden, Deutschland
Registration No. 21604

Experimental investigations of a magnetically driven Tornado-like vortex by means of Ultrasound-Doppler Velocimetry
Vogt, T.; Grants, I.; Eckert, S.; Gerbeth, G.
Abstract: The spin-up of a concentrated vortex in a liquid metal cylinder with a free surface is considered experimentally. The vortex is driven by two flow independent magnetic body forces. A continuously applied rotating magnetic field provides the source of the angular momentum. A pulse of about one order of magnitude stronger travelling magnetic field drives a converging flow that temporarily focuses this angular momentum towards the axis of the container. A highly concentrated vortex forms that produces a funnel-shaped surface depression. In this study we have used some modified settings for the UDV device in order to detect the vertical position of the free surface along the beam line. The main modification was a reduction of the echo detection sensitivity. In this way the echo from microscopic particles was blinded out. Instead, only the position of the strong echo from the free surface was detected and recorded. We explore experimentally the duration, the depth and the conditions of formation of this funnel.
Keywords: gas entrainment, bubble detection
  • Lecture (Conference)
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 26.-29.08.2014, Strasbourg, Frankreich
  • Contribution to proceedings
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 26.-29.08.2014, Strasbourg, Frankreich
    Proceedings of the 9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering
Registration No. 21603

Using XFELs to probe the interaction dynamics of ultra-intense lasers with solid-density matter
Cowan, T. E.; Kluge, T.; Huang, L.; Gutt, C.; Pelka, A.; Bussmann, M.
Abstract: The advent of intense coherent hard x-ray sources based on free electron lasers have opened a new era of ultrafast science. Facilities such as FLASH, LCLS, SACLA, and the under-construction European XFEL, will enable time and spatially resolved probing of atomic, molecular, chemical, biological and plasma dynamics, on the scale of fs and nm. Here we present theoretical concepts to make use of coherent x-ray scattering to probe ultra-intense laser-driven plasmas. In addition, status of the HIBEF User Consortium at the European XFEL will be presented.
Keywords: X-rays, XFEL, ultrafast science, relativistic plasmas
  • Invited lecture (Conferences)
    Graduate School of Engineering Seminar, Osaka University, 07.01.2014, Osaka, Japan
Registration No. 21602

The 22Ne(p,gamma)23Na reaction studied at LUNA: results from the germanium detector based part of the experiment
Bemmerer, D.
Abstract: The 22Ne(p,γ)23Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle is active in asymptotic giant branch stars as well as in novae and contributes to the nucleosythesis of neon and sodium isotopes. In order to reduce the uncertainties in the predicted nucleosynthesis yields, new experimental efforts to measure the 22Ne(p,γ)23Na cross section directly at the astrophysically relevant energies are needed.
The seminar talk will report on the recently concluded first phase of the 22Ne(p,γ)23Na experiment at LUNA. Using a windowless, isotopically enriched 22Ne gas target and two high-purity germanium detectors, selected, previously unobserved low-energy resonances were studied. The preliminary results will be summarized, and an outlook on the second phase of the experiment with a 4pi summing detector will be given.
  • Invited lecture (Conferences)
    INFN Laboratori Nazionali del Gran Sasso Seminar, 10.12.2014, Assergi, Italien
Registration No. 21601

Separation of ultrafine particles by two-liquid flotation: Selectivity and process behavior analysis
Rudolph, M.; Peuker, Urs A.
Abstract: It is well known, that for conventional froth flotation techniques the processing of ultrafine mineral particles is generally inefficient and results in rather low-grade concentrates and relatively high losses of valuable minerals. Therefore, the investigation of other possible methods, which can selectively separate such fine particle systems effectively, is of considerable interest.
In this study, the application of two-liquid flotation, a flotation-related process using oil droplets instead of air bubbles, is investigated as a possible processing strategy for the separation of ultrafine particle systems. The investigation involves the testing of the two-liquid flotation technique as simple laboratory-scale batch trials and moreover, the up-scaling to a semi-continuous process by using a modified lab scale flotation column. Magnetite and quartz particles, with particle sizes below 10 μm respectively, as academic mineral mixture and iso-octane and water as the two immiscible liquid phases are chosen for the experiments. To manipulate the wettability of the magnetite particles as well as the interfacial tension of the oil/water interfaces, surface active reagents of fatty acid basis are introduced in the system. The selectivity of the process is characterized by determining the removal of magnetite particles from the aqueous suspension through selective accumulation at the oil/water interface or extraction into the oil phase, respectively. Operational parameters including pH of the aqueous suspension, additional electrolyte addition and surfactant type as well as dosage are varied in order to maximize the efficiency and stability of the process.

Keywords: ultra fine particle prossessing, flotation methods, two-liquid flotation
  • Lecture (Conference)
    XXVII International Mineral Processing Congress, 20.-24.10.2014, Santiago de Chile, Chile
Registration No. 21600

Mineralization derived from felsic magma? A case study on Zr-Nb-REE deposits in Western Mongolia
Kempe, U.; Möckel, R.
Abstract: The genesis of unconvential Zr-Nb-REE deposits is still under discussion. The mineralization of the Khalzan Buregte and surrounding massifs in western Mongolia is introduced as a case study. We present data showing that the enrichment of valuable elements is mainly due to multistage metasomatic alteration, although the primary contents are quite high as well. The theory of secondary enrichment is also widened on other deposits in the Erzgebirge mountains, Saxony/Germany for comparison.
Keywords: rare earth elements REE, Khalzan Buregte, Mongolia
  • Invited lecture (Conferences)
    13th Freiberg Short Course in Economic Geology - Rare earth element deposits, 08.-12.12.2014, Freiberg, Deutschland
Registration No. 21598

Background intercomparison with an active shielded HPGe detector extended to Freiberg mine in Germany
Szücs, T.; Bemmerer, D.; Reinhardt, T. P.; Schmidt, K.; Takács, M. P.; Wagner, L.
Abstract: A key requirement for underground nuclear astrophysics experiments is the very low background level in germanium detectors. The reference for these purposes is the world’s so far only underground accelerator laboratory for nuclear astrophysics, LUNA. LUNA is located deep underground in the Gran Sasso laboratory in Italy, shielded from cosmic rays by 1400m of rock. The background at LUNA was studied in detail using an escape-suppressed Clover-type HPGe detector [1]. Exactly the same detector was subsequently transported to the Felsenkeller underground laboratory in Dresden, shielded by 45m of rock, and the background was shown to be only a factor of three higher than at LUNA when comparing the escape-suppressed spectra, with interesting consequences for underground nuclear astrophysics [2]. As the next step of a systematic study of the effects of a combination of active and passive shielding on the cosmic ray induced background, this detector has recently been brought to the "Reiche Zeche" mine in Freiberg, Germany, shielded by 150m of rock.
The data available with one and the same actively shielded HPGe detector at the Earth's surface and below 45, 150, and 1400m of rock allow getting a general understanding of the effects of active shielding with depth.
– Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (HGF VH-VI-417).

[1] T. Szücs et al., Eur. Phys. J. A 44, 513 (2010).
[2] T. Szücs et al., Eur. Phys. J. A 48, 8 (2012).

Keywords: underground, nuclear astropysics, gamma background
  • Poster
    13th international symposium on Nuclei in the Cosmos (NIC-XIII), 07.-11.07.2014, Debrecen, Hungary
Registration No. 21597

Determination of level widths in 15N using nuclear resonance fluorescence
Szücs, T.; Bemmerer, D.; Caciolli, A.; Fülöp, Zs.; Massarczyk, R.; Michelagnoli, C.; Reinhardt, T. P.; Schwengner, R.; Takács, M. P.; Ur, C. A.; Wagner, A.; Wagner, L.
Abstract: The stable nucleus 15N is the mirror of the astrophysically important 15O, the product of the slowest reaction in the hydrogen burning CNO cycle, which therefore determine the production rate of the cycle.
Most of the 15N level widths below the nucleon emission thresholds are known from just one nuclear resonance fluorescence (NRF) measurement published more than 30 years ago, with limited precision in some cases [1]. A recent experiment with the AGATA demonstrator array aimed to determine level widths using the Doppler Shift Attenuation Method (DSAM) in 15O and 15N populated in the 14N + 2H reaction. In order to set a benchmark value for the upcoming AGATA demonstrator data, the widths of several 15N levels have been studied with high precision using the bremsstrahlung facility gELBE [2] at the electron accelerator of Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The precision of our new dataset are on a 10% level for the weak transitions, which have 60% and 100% error bars in the old dataset. The preliminary data seem to confirm the earlier NRF data.
- Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (HGF VH-VI-417).

[1] R. Moreh et al., Phys. Rev. C 23, 988 (1981).
[2] R. Schwengner et al., Nucl. Inst. Meth. A 555, 211 (2005).

Keywords: Level widths, nuclear astrophysics, bremsstrahlung
  • Poster
    13th international symposium on Nuclei in the Cosmos (NIC-XIII), 07.-11.07.2014, Debrecen, Hungary
  • Poster
    Fifteenth International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS15), 25.-29.08.2014, Dresden, Germany
Registration No. 21596

Background intercomparison with escape-suppressed germanium detectors in underground mines
Szücs, T.; Bemmerer, D.
Abstract: A key requirement for underground nuclear astrophysics experiments is the very low background level in germanium detectors underground. The reference for these purposes is the world’s so far only underground accelerator laboratory for nuclear astrophysics, LUNA. LUNA is located deep underground in the Gran Sasso laboratory in Italy, shielded from cosmic rays by 1400 m of rock. The background at LUNA was studied in detail using an escape-suppressed Clover-type HPGe detector [1]. Exactly the same detector was subsequently transported to the Felsenkeller underground laboratory in Dresden, shielded by 45 m of rock, and the background was shown to be only a factor of three higher than at LUNA when comparing the escape-suppressed spectra, with interesting consequences for underground nuclear astrophysics [2]. As the next step of a systematic study of the effects of a combination of active and passive shielding on the cosmic ray induced background, this detector is now being brought to the "Reiche Zeche" mine in Freiberg/Sachsen, shielded by 150 m of rock. The data from the Freiberg measurement will be shown and discussed. – Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (HGF VH-VI-417).

[1] T. Szücs et al., Eur. Phys. J. A 44, 513 (2010)
[2] T. Szücs et al., Eur. Phys. J. A 48, 8 (2012)

Keywords: Underground, nuclear astrophysics, low background
  • Lecture (Conference)
    DPG Frühjahrstagung, Fachgruppe Hadronen und Kerne, 21.03.2014, Frankfurt, Germany
Registration No. 21595

Gamma-ray width measurements in 15N at the ELBE nuclear resonance fluorescence setup
Szücs, T.; Bemmerer, D.; Massarczyk, R.; Schwengner, R.; Takács, M.; Wagner, L.
Abstract: The stable nucleus 15N is the mirror of the astrophysically important 15O, compound nucleus of the leading reaction of the Bethe-Weizsäcker cycle of hydrogen burning. Most of the 15N level widths below the neutron and proton emission thresholds are known from just one nuclear resonance fluorescence (NRF) measurement published more than 30 years ago, with unsatisfactory precision on some cases [1]. A recent experiment with the AGATA demonstrator array aimed to determine level widths with the Doppler Shift Attenuation Method (DSAM) in 15O and 15N populated in 14N + 2H reaction. In order to set a benchmark value for the upcoming AGATA demonstrator data, the widths of several 15N levels are being studied using the bremsstrahlung facility γELBE at the electron accelerator of Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The γELBE experiment and its preliminary results will be presented. – Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (HGF VH-VI-417).

[1] R. Moreh et al., Physical Review C 23, 988 (1981)

Keywords: Nuclear astrophysiscs, level widths, gamma scattering, bremsstrahlung
  • Lecture (Conference)
    DPG Frühjahrstagung, Fachgruppe Hadronen und Kerne, 20.03.2014, Frankfurt, Germany
Registration No. 21594

Underground nuclear astrophysics (Dubna lecture)
Szücs, T.
Abstract: The very low background level is a key requirement for underground nuclear astrophysics experiments. The reference for these purposes is the world’s so far only underground accelerator laboratory for nuclear astrophysics, LUNA. LUNA is located deep underground in the Gran Sasso laboratory in Italy, shielded from cosmic rays by 1400m of rock.
This talk presents the need and the advantages of an underground setting. It covers also new findings, regarding active shielding at underground settings, leading to have the possibility to perform nuclear astrophysics experiments with sufficient precision also at shallow underground.
Finally the recent nuclear astrophysics related experiments performed at the surface, at LUNA, and at different underground depths will be presented.

Keywords: Underground, Nuclear Astropysics, low background
  • Invited lecture (Conferences)
    Helmholtz International Summer School "NUCLEAR THEORY AND ASTROPHYSICAL APPLICATIONS", 29.07.2014, Dubna, Russia
Registration No. 21593

Strategische Metalle und Mineralien - die BMBF Fördermaßnahme r³
Anke Dürkoop, G. G.
Abstract: Übersicht zur r³ Fördermaßnahme (Präsentation auf PIUS Länderkonferenz)
  • Invited lecture (Conferences)
    PIUS Länderkonferenz 2014, 02.07.2014, Frankfurt am Main, Deutschland
Registration No. 21588

Trace elements - small concentrations, great importance!
Frenzel, M.
Abstract: A lecture was given to school students (~ ages 16 - 18) about the industrial importance of certain trace elements occurring in different raw materials, and the methods used to study their behaviour in the related geological systems.
Keywords: Trace elements, geology, analytics
  • Lecture (others)
    Akademische Woche 2014, 13.02.2014, Meißen, Germany
Registration No. 21584

Trace elements - small concentrations, great importance
Frenzel, M.
Abstract: A presentation was given to school students (~ ages 16 - 18) on some aspects of trace elements occurring in different kinds of raw materials, their industrial importance, the uncertainties about their geological behaviour, and the methods used to study their occurrence and distribution in geological systems.
Keywords: Trace elements, Analytical techniques
  • Lecture (others)
    Akademische Woche, 13.02.2014, Meißen, Germany
Registration No. 21582

Selektive Trennung feinstdisperser Partikelsysteme mit Hilfe von Flotationstechniken
Schützenmeister, L.
Abstract: Deutschland ist eine der am höchsten technologisierten Industrienationen der Welt und liegt mit einem Rohstoffverbrauch von 200 kg pro Kopf und Tag ebenfalls mit an der Spitze [1]. Das Umweltbundesamt hat jedoch aus diesem Grund im Jahr 2012 nicht nur auf die damit verbundenen Umweltschäden hingewiesen sondern nachdrücklich fest-gestellt, dass Deutschland in der Zukunft sparsamer mit seinen Ressourcen umgehen muss. Anderenfalls wird es in der Zukunft aufgrund wachsender Rohstoffpreise seine weltweite Führungsrolle verlieren [1]. Die modernen High-Tech-Produkte wie Smart-phones, Tablet-PCs und LEDs aber insbesondere auch „grüne“ Technologien wie So-larzellen, Elektromotoren und Windkraftanlagen sind alle eng mit dem Verbrauch selte-ner Metalle wie Gallium, Germanium und Indium sowie den sogenannten seltenen Er-den verknüpft [2,3]. Im Zuge des wirtschaftlichen Aufschwungs der Schwellenländer nimmt jedoch der Rohstoffbedarf weltweit rasant zu. Eine herausragende Rolle spielt dabei China, da sich dort über 97 % der weltweiten Förderstätten für seltene Erden befinden [1]. Aufgrund des wachsenden Eigenbedarfs hat China jedoch den Export seltener Erden bereits zwischen 2009 und 2012 um 38 % reduziert, Tendenz steigend [seltene Erden]. Gleichzeitig wird prognostiziert, dass sich der weltweite Bedarf bspw. an Neodym und Dysprosium in den nächsten 25 Jahren um ca. 700 und 2600 % stei-gern wird [4]. Dabei ist der Preis für eine Tonne Neodym, wie sie bspw. für die Herstel-lung des Elektromagneten eines leistungsstarken, getriebelosen Offshore-Windrades benötigt wird, zwischen 2005 und 2012 bereits von 25.000 auf rund 700.000 US-Dollar gestiegen [3]. Zwar werden auch heute noch neue, reichhaltige Lagerstätten entdeckt, wie zum Beispiel durch japanische Forscher im Pazifik im Jahre 2013, jedoch ist die Gewinnung speziell in großen Tiefen auf offenem Meer mit großen Problemen verbun-den [3].
Diese Faktoren haben in den letzten Jahren zu einem Umdenken in der Ressourcen-politik geführt. So wurde von der Bundesregierung im Jahre 2011 das Helmholtz-Institut für Ressourcentechnologie in Freiberg gegründet, mit dem Ziel neue Technolo-gien zu entwickeln, welche eine effizientere Bereitstellung und Nutzung mineralischer und metallischer Rohstoffe ermöglichen [2]. Das Hauptziel der Forschung liegt sowohl in der Nutzbarmachung komplexer Erze, wie sie auch in Deutschland lagern, deren Aufbereitung mit bisherigen Technologien jedoch nicht wirtschaftlich ist, als auch in der Entwicklung effizienter Recyclingmethoden für verbrauchte Rohstoffe [2]. Eine bedeu-tende Rolle nimmt dabei die Weiterentwicklung von Flotationstechniken, speziell auch der Kolonnenflotation, ein.
Seit Beginn der achtziger Jahre wurden insbesondere zur Nachanreicherung zuneh-mend Flotationskolonnen anstelle von Flotationszellen eingesetzt [5]. Diese zeichnen sich durch ein verbessertes Wertstoffausbringen und Anreicherungsvermögen, niedri-gere Anschaffungs- und Betriebskosten, geringeren Verschleiß und geminderten Platzbedarf aus [6].
Die heute geforderten Aufbereitungsziele erfordern in der Regel eine Zerkleinerung des Materials in den Feinstkornbereich. Klassische Schaumflotation versagt jedoch ab Korngrößen von x < 20 zunehmend [7]. Eine Lösung dieses Problems kann in der Anwendung der sogenannten Flüssig-Flüssig-Flotation in Flotationskolonnen liegen. Dabei wird anstelle von Luft eine organische Phase zur Flotation eingesetzt.
Die vorliegende Arbeit befasst sich daher mit der Konzeptionierung, dem Bau und dem Einfahren einer Versuchsanlage für Schaum- und Flüssig-Flüssig-Flotation. Weiterhin werden Grundlagenuntersuchungen, welche für einführende Flotationstests an der neuen Kolonne benötigt wurden, beschrieben.

Keywords: Flotation, extraction, particles, disperse systems
  • Bachelor thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Tom Leistner, Dr. Martin Rudolph
    77 Seiten
Registration No. 21581

Flüssig-Flüssig Flotation in einer Tropfensäule – Tropfendispersitätsanalyse und Selektivität im System Magnetit-Quarz
Müller, M.
Abstract: Die selektive Extraktion von hydrophobisierten Partikeln in einer Tropfensäule ist eine Heterokoagulationstrennung, wie die Flotation. Dieser neuartige Prozess soll als Erweiterung der Flotation, insbesondere für Partikel kleiner 10 µm dienen.
In dieser Masterarbeit ist die bestehende Tropfensäule am Institut für Mechanische Verfahrenstechnik und Aufbereitungstechnik der TU Bergakademie Freiberg zu erweitern, sodass die Tropfen mit einer kamerabasierten Methode im einfachen und doppelten Kreislauf als Funktion der Zeit und unter Berücksichtigung von grenzflächenaktiven Substanzen quantifiziert werden können. Hierfür wird ein Messfenster konzipiert und in die bestehende Anlage integriert. Es soll gezeigt werden, wie die Prozessregime die Tropfendispersität über der Zeit beeinflussen.
Des Weiteren wird die selektive Trennung von Magnetit und Quarz als akademisches Stoffsystem im Scheidetrichter untersucht. Hierfür sind die natürlichen Minerale auf eine mittlere Partikelgröße von 10 µm zu konfektionieren. Als Ergebnis der Trennung im Scheidetrichter unter Variation der hydrophobisierenden Substanzen (Fettsäuren für Magnetit, bzw. Amine für Quarz), sowie von Reglern (pH Wert ändernd) wird das erfolgreichste Reagenzregime auf erste Versuche für Trennungen in der Tropfensäule zum Ende der Arbeit übernommen und untersucht. Zudem wird das natürliche Magnetit in separaten Versuchen ersetzt mit synthetischen gefällten Magnetit Nanopartikeln.
Die Untersuchungen erfolgen am Institut MVTAT in Kooperation mit dem Helmholtz-Institut Freiberg für Ressourcentechnologie des Helmholtz-Zentrums Dresden-Rossendorf.

Keywords: flotation, extraction, drop formation, magnetite, quartz
  • Master thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Tom Leistner, Dr. Martin Rudolph
    86 Seiten
Registration No. 21579

Flotation eines Seltene-Erden-Erzes mit dem Wertmineral Eudialyt
Ludwig, K.
Abstract: Bei der Herstellung moderner elektronischer Produkte sind Erze mit Seltenen Erden unverzichtbar. Ein Beispiel hierfür ist eudialythaltiges Erz, welches das chemische Element Yttrium beinhaltet. Yttrium wird z.B bei der Produktion von Leuchtstoffen, Laserkristallen, Keramiken für Zündkerzen und Lambda-Sonden verwendet. Daneben wird es zur Steigerung der Festigkeit in einigen Legierungen genutzt. Der Anteil an Yttrium im Eudialyt-Mineral ist sehr gering. Eudialyt selbst ist außerdem stark in anderen silikatischen Mineralen verwachsen. Zudem ähneln diese silikatischen Minerale aufgrund ihrer chemischen Struktur dem Eudialyt. Die Gewinnung und Anreicherung dieses Wertstoffes aus dem Erz ist daher eine Herausforderung für die Aufbereitungsindustrie. Eine Dichtesortierung ist aufgrund der ähnlichen Dichten der einzelnen Minerale nicht möglich. Zurzeit untersucht man zwei Trennverfahren hinsichtlich ihrer Brauchbarkeit: Magnetscheidung und Flotation. Bei der Flotation spielen die Wechselwirkungen zwischen den einzelnen Mineralen und den zugesetzten Reagenzien eine entscheidende Rolle. Letztere bieten Ansatzmöglichkeiten für eine Steuerung der Flotation. Daher werden auch gegenwärtig immer wieder neue Reagenzien entwickelt und damit neue flotative Verfahren geschaffen. Im Rahmen dieser Arbeit ist die Aufbereitung eines eudialythaltigen Erzes aus Norra Kärr in Schweden mit Hilfe der Flotation zu untersuchen. Dabei wird der Einfluss von verschiedenen Reagenzien, der sogenannten Sammler und Drücker, auf die Anreicherung der einzelnen Bestandteile des Aufgabegutes analysiert.Weiterhin werden die Flotationsergebnisse von entschlammten und nicht entschlammten Proben verglichen. Die Versuche finden sowohl in saurem als auch in basischem Milieu statt. Die Zusammensetzung des Aufgabegutes und der Konzentrate wird mit Hilfe der
Röntgendiffraktometrie ermittelt.

Keywords: eudialyte, rare earth elements, Flotation, aegirine, collector, hydroxamate, oleate
  • Bachelor thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Dr. Martin Rudolph
    84 Seiten
Registration No. 21578

Charakterisierung partikelhaltiger Öl/Wasser-Emulsionen - Phasenzusammensetzung und Stabilitätsbetrachtung
Landgraf, K.
Abstract: Seit Jahrzehnten steigt die Nachfrage nach Rohstoffen und die Anforderung aus diesen einen Wertstoff möglichst rein anzureichern. Durch die zunehmende Rohstoffknappheit werden längst sekundäre Rohstoffquellen genutzt, aber auch primäre Quellen, in welchen der Wertstoff nur zu geringen Anteilen und in sehr hohen Verwachsungsgraden vorkommt. Für den Aufbereitungsprozess ist es von Nöten den Rohstoff so weit aufzuschließen, dass der Wertstoff getrennt von dem Bergematerial vorliegt. Bei einem stark verwachsenen Material entsteht dadurch ein hoher Anteil an Feingut, welches in nachgeschalteten Sortierprozessen Probleme bereitet.
Etabliert zur Feinstgutaufbereitung sind die Verfahren der Heterokoagulationstrennung, in denen Berge- und Wertstoffmaterial auf Grund verschiedener physikalischer Eigenschaften sortiert werden [1], [2], [3].
Die Schaumflotation ist der am häufigsten angewandte Prozess, wobei Partikel mit einem Durchmesser zwischen 5 und 5000 mm flotiert werden können [4]. Am effizientesten werden Partikel im Größenbereich zwischen 10 mm und 100 mm [5], [6], [7] erfasst. Damit kann in diesem Größenbereich eine hohe Produktqualität erzielt werden.
Partikel, die kleiner als 10 mm sind, bereiten im Flotationsprozess Probleme und wurden darum meist vor der Flotation abgetrennt. Der darin enthaltene Wertstoff kann somit nicht gewonnen werden.
Um auch die im Feinstanteil vorkommenden Rohstoffe nutzbar zu machen, wurde für einige Anwendungen der Schaumflotationsprozess modifiziert.
Beispielsweise wurde die Flüssig-Flüssig-Flotation entwickelt, bei der die feinen Feststoffpartikel anstatt mit Luftblasen, mit einer zweiten fluiden, mit Wasser nicht mischbare Phase koagulieren. Dies kann den Trennerfolg im Aufbereitungsprozess verbessern.
Noch setzten sich diese Prozesse in der großtechnischen Aufbereitung nicht durch, unter anderem da sie kostenintensiv sind und der Einsatz von Öl umweltproblematisch ist. Des Weiteren entsteht im Verlauf der Flüssig-Flüssig-Flotation eine Emulsion, die durch die feinen Partikel stabilisiert wird. Ein Sortierprozess ist erfolgreich, wenn es gelingt die Feststoffpartikel selektiv auszutragen und die entstehende Emulsion zu brechen. Erst dann liegen die Wertstoffpartikel getrennt von den fluiden Phasen und dem Bergematerial vor.
Um weiterhin den Rohstoffbedarf decken zu können, sollten sich Bemühungen darauf richten, diese Verfahren zu optimieren, um sie in der Aufbereitung hoch aufgeschlossener Rohstoffe einsetzen zu können.
Diese Arbeit handelt von partikelstabilisierten Emulsionen, die in einem Flüssig-Flüssig-Flotationsprozess entstehen. Mineralisches Magnetit und Quarz mit einer Partikelgröße dP,80 < 10 mm [8] werden eingesetzt und lagern sich im Versuchsverlauf an Öltropfen, die in Wasser dispergiert sind und stabilisieren diese. Die so entstehenden Emulsionen werden von der wässrigen Phase getrennt und Untersuchungen zu Phasenzusammensetzung sowie Stabilität der Emulsionen durchgeführt.
Dies soll dazu beitragen, Erkenntnisse zu deren Handhabung und Destabilisierung zu erhalten und somit auf lange Sicht die Anwendbarkeit der ölbasierten Flotationsprozesse zu ermöglichen [2], [3], [6], [8], [9].

Keywords: Flotation, extraction, Emulsion, colloidal stability
  • Bachelor thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Tom Leistner, Dr. Martin Rudolph
    119 Seiten
Registration No. 21577

Oberflächenladungseigenschaften von synthetischen Selten-Erden Karbonaten und Selten-Erden Phosphaten und Wirkung von Sammlern und Drückern
Kratzsch, R.
Abstract: Das Helmholtz-Institut Freiberg für Ressourcentechnologie wurde im August 2011 als Institut des Helmholtz-Zentrum Dresden-Rossendorf gegründet um sich ressourcentechnologischen Fragestellungen für primäre und sekundäre Rohstoffe mit strategischen Metallen zu widmen. Die Abteilung Aufbereitung befasst sich insbesondere mit der Trennung von feinen Partikeln basierend auf unterschiedlichen Benetzungseigenschaften der Oberflächen, wie dem Prozess der Flotation. Im Fokus bzgl. Wertstoffen liegen insbesondere die Metalle der Seltenen-Erden, welche wichtig sind für High-Tech Anwendungen und somit essentiell für die deutsche Industrie.
In dieser studentischen Arbeit sollen die Oberflächenladungseigenschaften von synthetischen Selten-Erden Karbonaten (SEE-CO3) und Selten-Erden Phosphaten (SEE-PO4) im Vergleich zu Calciumcarbonat und Bariumcarbonat systematisch untersucht werden. Die physikochemischen Eigenschaften sind über den pH-Wert zu variieren. Die Wirkung von Fettsäuren als Sammler, sowie von Ligninsulfonat als Drücker sind zu untersuchen. Die Partikel sind granulometrisch zu beschreiben.
Die Untersuchungsmethoden umfassen hierbei:
- Mikroflotationsuntersuchungen in einer Hallimondröhre
- Zeta-Potential Bestimmung mit Zetasizer Nano ZS
- Partikelgrößenmessung mit Laserbeugung
- Bestimmung der spezifischen Oberfläche mit der BET-Methode
- Dichtebestimmung mit Pyknometer
- Schwingungsspektroskopie mit ATR-FTIR
- Adsorptionsuntersuchungen unter Verwendung von UV/VIS
Die Arbeit umfasst zudem eine begleitende Literaturrecherche unter Berücksichtigung aktuellster wissenschaftlicher Erkenntnisse zum Thema.

Keywords: Flotation, rare earth elements, collector, depressant, zeta potential
  • Bachelor thesis
    TU Bergakademie Freiberg, 2013
    Mentor: Dr. Martin Rudolph
    53 Seiten
Registration No. 21576

Vergleich von Carbonsäuren, Alkylhydroxamaten und Sarkosinaten als Sammler für die Apatitflotation
Klöpfel, K.
Abstract: Am Helmholtz-Institut Freiberg für Ressourcentechnologie werden Technologien entwickelt, um die Verfügbarkeit wirtschaftskritischer mineralischer Rohstoffe für die deutsche und europäische Industrie zu sichern. Ein wichtiges Wertmineral ist Apatit, aus dem Phosphor, sowie in Spuren Seltene Erden Metalle gewonnen werden kann. Die Flotation spielt hierbei eine wichtige Rolle, um Silikate und Carbonate als Gangminerale abzutrennen. Üblicherweise kommen Carbonsäuresalze als Sammler für die direkte Flotation zum Einsatz, wobei deren Selektivität besonders gegenüber den Carbonaten gering ist. Es existieren mit den Sarkosinaten und Hydroxamaten molekular ähnliche Substanzen, die in dieser Arbeit bzgl. Ihres Flotierbarkeitsverhalten zu Apatit untersucht werden sollen. Die Wirkung der zu vergleichenden Sammler wird in dieser Arbeit mit Hilfe von Oberflächenspannungsmessungen, Zeta-Potential-Bestimmungen sowie Mikroflotationsuntersuchungen an der reinen Mineralphase des Fluor-Apatits untersucht.
Es ist zudem die aktuelle Literatur zum Thema zu recherchieren und zusammenzutragen.

Keywords: flotation, apatite, collector, sodium oleate, sodium sarcosinate, potassium octyl hydroxamate, zeta potential
  • Bachelor thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Dr. Martin Rudolph
    72 Seiten
Registration No. 21575

Partikelsonden Rasterkraftmikroskopie - Untersuchung der hydrophoben Eigenschaften von Mineraloberflächen im Kontext der Flotation
Kaminsky, P.
Abstract: Das Helmholtz-Institut Freiberg für Ressourcentechnologie führt Grundlagenforschungen zur flotativen Aufbereitung von Erzen durch. Ein wichtiger Aspekt der Flotation ist die selektive Hydrophobisierung von Mineralen des Erzes. Der attraktive hydrophobe Effekt ist hierbei verantwortlich für die Anhaftung von selektiven Mineralen an Gasblasen und somit der Abtrennung dieser Mineralphasen aus einer gemahlenen Erzsuspension. Es wird eine Messmethode entwickelt, die es erlauben soll auf Mineralschliffen eines Erzes hydrophobe Eigenschaften ortsaufgelöst zu bestimmen. Grundbestandteil ist dabei die Partikelsonden-Rasterkraftmikroskopie (CP-AFM).
Diese Masterarbeit soll die CP-AFM Methode an grobkristallinen Magnetit- und Quarzproben unter Verwendung selektiver Sammler untersuchen. Die Ergebnisse dieser Hydrophobizitätsmessung sollen im Kontext gesetzt werden zu Mikroflotationsuntersuchungen der Stoffsysteme. Es soll die CP-AFM Methode kritisch analysiert werden. Neben den genannten Methoden sind die Stoffsysteme bzgl. der Sammlerwechselwirkung und der Benetzung näher zu untersuchen. Der aktuelle Stand der Forschung soll ebenfalls in einer Literaturrecherche erfasst und zusammengefasst werden.

Keywords: AFM, hydrophic interactions, Magnetite, quartz, Flotation, zeta potential, collector
  • Master thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Dr. Martin Rudolph
    120 Seiten
Registration No. 21574

Structural changes in amorphous GexSiOy on the way to nanocrystal formation
Nyrow, A.; Sternemann, C.; Sahle, Ch J.; Hohl, A.; Zschintzsch-Dias, M.; Schwamberger, A.; Mende, K.; Brinkmann, I.; Sala, M. Moretti; Wagner, R.; Meier, A.; Voelklein, F.; Tolan, M.
Abstract: Temperature induced changes of the local chemical structure of bulk amorphous GexSiOy are studied by Ge K-edge x-ray absorption near-edge spectroscopy and Si L-2/3-edge x-ray Raman scattering spectroscopy. Different processes are revealed which lead to formation of Ge regions embedded in a Si oxide matrix due to different initial structures of as-prepared samples, depending on their Ge/Si/O ratio and temperature treatment, eventually resulting in the occurrence of nanocrystals. Here, disproportionation of GeOx and SiOx regions and/or reduction of Ge oxides by pure Si or by a surrounding Si sub-oxide matrix can be employed to tune the size of Ge nanocrystals along with the chemical composition of the embedding matrix. This is important for the optimization of the electronic and luminescent properties of the material.
Keywords: KeyWords Plus:VISIBLE PHOTOLUMINESCENCE; GE NANOCRYSTALS; ALLOY-FILMS; SILICON NANOCRYSTALS; THIN-FILMS; MICROCRYSTALS; MEMORY; LUMINESCENCE; EXCITATIONS; DEFECTS Registration No. 21573

Investigation of the surface free energy of several minerals by iGC (inverse gas chromatography) and correlation with floatability
Hartmann, R.
Abstract: It is well known that the flotation process separates particles with different wettability dispersed in water. The fundamental physical-chemical property therefore is the specific surface free energy of the mineral surface which together with the specific surface free energy of water causes wettability phenomena besides the surface morphology (e.g. roughness). Inverse Gas Chromatography is a tool which enables determination of the specific surface free energy of powders. There are a few reports on the correlation of flotation response and surface free energy, however the crucial problem is that the flotability is determined in water and the surface free energy is evaluated in the dried powder phase. To determine the effect flotation chemicals have on the specific surface free energy of minerals it is important to investigate the preparation of the dried powder after conditioning with the chemicals in water.
In this Master thesis different minerals (quartz, apatite and magnetite) and ionic collectors (sodium oleate and dodecyl ammonium acetate) with crucially different surfactant adsorption mechanisms will be used to determine floatability and specific surface free energy with different steps of preparation, i.e. washing with mother liquid only or further with solvents with another polarity. The flotation response and the specific surface free energy shall be put in context. It is important to find the proper presentation of the surface free energy components and define a quantitative description of hydrophobicity. It should finally, based on the results, be described in which way flotation samples should be treated for iGC measurements.
The literature is to be researched and summarized for the latest information on the topic.

Keywords: inverse gas chromatography, flotation, surface free energy, wettability, hydrophobicity
  • Master thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Dr. Martin Rudolph
    113 Seiten
Registration No. 21572

Charge trapping of Ge-nanocrystals embedded in TaZrOx dielectric films
Lehninger, D.; Seidel, P.; Geyer, M.; Schneider, F.; Klemm, V.; Rafaja, D.; von Borany, J.; Heitmann, J.
Abstract: Ge-nanocrystals (NCs) were synthesized in amorphous TaZrOx by thermal annealing of co-sputtered Ge-TaZrOx layers. Formation of spherical shaped Ge-NCs with small variation of size, areal density, and depth distribution was confirmed by high-resolution transmission electron microscopy. The charge storage characteristics of the Ge-NCs were investigated by capacitance-voltage and constant-capacity measurements using metal-insulator-semiconductor structures. Samples with Ge-NCs exhibit a maximum memory window of 5 V by sweeping the bias voltage from −7 V to 7 V and back. Below this maximum, the width of the memory window can be controlled by the bias voltage. The fitted slope of the memory window versus bias voltage characteristics is very close to 1 for samples with one layer Ge-NCs. A second layer Ge-NCs does not result in a second flat stair in the memory window characteristics. Constant-capacity measurements indicate charge storage in trapping centers at the interfaces between the Ge-NCs and the surrounding materials (amorphous matrix/tunneling oxide). Charge loss occurs by thermal detrapping and subsequent band-to-band tunneling. Reference samples without Ge-NCs do not show any memory window Registration No. 21569

Towards a novel THz-based monitor for sub picosecond electron bunches working at MHz repetition rates and low bunch charges
Kovalev, S.; Green, B.; Golz, T.; Kuntzsch, M.; Fisher, A.; Stojanovic, N.; Gensch, M.
Abstract: Femtosecond level diagnostic and control of sub-picosecond electron bunches is an important topic in modern accelerator research. At the same time new quasi-cw linear electron accelerators are the drivers of many future 4th Generation lightsources such as X-ray free electron lasers. A high duty cycle, high stability and online pulse to pulse diagnostic of these new accelerators are crucial ingredients to the success of these large scale facilities. A novel THz based online monitor concept is presented that has the potential to give access to pulse to pulse information on bunch form, arrival time and energy at high repetition rate and down to sub pC charges. It has been shown experimentally that pulse to pulse arrival time measurements can be used to perform high temporal resolution and dynamic range experiments, removing the influence of synchronization problems between the accelerator and external laser systems.
  • Poster
    4th workshop on longitudinal instrumentation for future accelerators, 15.-16.01.2015, Villigen, Switzerland
Registration No. 21567

Re-Green Indicator System
Dirlich, S.
Abstract: The presentation deals with the development of an indicator system for the sustainability assessment of green policies dedicated to retrofitting of buildings, urban districts, and entire cities.
Based on existing building sustainability assessment schemes a specific indicator system is developed meeting the requirements of the Re-Green project.
The flexible and modular structure of the system allows an adaptation of the sustainability assessment to the particular circumstances and conditions of the region/city to be evaluated.

Keywords: sustainability assessment; green building; retrofit
  • Invited lecture (Conferences)
    FutureBuild 2014, 05.-06.11.2014, Sheffield, Großbritannien
Registration No. 21566

High magnetic field study of the Dy2Fe17Hx compounds with x = 0-3.8
Isnard, O.; Andreev, A. V.; Heczko, O.; Skourski, Y.
Abstract: The Dy2Fe17Hx compounds crystallizing in a hexagonal Th2Ni17-like structure are studied on aligned powder by magnetization measurements carried out in steady (up to 5 T) and pulsed (60 T) magnetic fields at 4.2-300 K. Dy2Fe17 is a ferrimagnet with TC = 375 K and a spontaneous moment of 16.5 μB/f.u. Magnetization curves recorded for two different crystal orientations for Dy2Fe17Hx polycrystalline oriented samples show that the insertion of hydrogen in the Dy2Fe17 crystal lattice significantly modifies the magnetization, Curie temperature and intersublattice exchange interactions of the Dy2Fe17 phase. The high-field behavior of Dy2Fe17 is compared with that of its hydrides derivatives. Despite different types of magnetic anisotropy, the high-field behavior of the hydrides and the parent compound is qualitatively similar. Depending upon the composition, they can exhibit easy plane or else conical type anisotropy as for x = 0 and 3, respectively. The low temperature spontaneous magnetization exhibits a moderate composition dependence, it first decreases continuously upon increasing the hydrogen composition up to x = 3 then slightly increases for x = 3.8 reflecting the Fe sublattice evolution. A mean Fe moment of about 2.1 μB is derived for Dy2Fe17H3.8 composition, this magnetization value is close to that of the original Dy2Fe17 compound. It is found that the intersublattice coupling between the Fe and Dy sublattices is reduced as illustrated by the decrease of the nDy-T coefficient from about 3.3 down to 2.82 T f.u./μB for Dy2Fe17 and Dy2Fe17H3.8, respectively. Registration No. 21563

Highly transparent and conductive Al-doped ZnO films synthesized by pulsed laser co-ablation of Zn and Al targets assisted by oxygen plasma
You, Q.; Cai, H.; Gao, K.; Hu, Z.; Guo, S.; Liang, P.; Sun, J.; Xu, N.; Wu, J.
Abstract: Highly optically transparent and electrically conductive Al-doped ZnO (AZO) thin films were deposited by pulsed laser co-ablation of a Zn target and an Al target in an oxygen plasma. Zn ablation resulted in the reactive deposition of ZnO films assisted by the plasma, while Al ablation provided the growing ZnO films with Al dopants. The morphology, composition and structure as well as the optical and electrical properties were characterized and the effects of Al doping and annealing treatment were investigated. The deposited AZO films have a hexagonal wurtzite structure with deteriorated crystal quality which can be improved by annealing. The AZO films are highly transparent from ultraviolet up to 1450 nm and present an obvious blue shift in absorption edge and a widening of band gap compared with undoped ZnO. The electrical properties were also improved after annealing with the resistivity decreasing by over two orders of magnitude because of the increase of free carrier concentration. The variation in the carrier concentration also affects the absorption edge and the band gap of the films as well as the transparency in the infrared region. Meanwhile, this method offers an approach for in-situ doping preparation of other doped compound films with different dopant concentrations.
Keywords: Al-doped ZnO; Co-ablation deposition; Electrical properties; In-situ doping; Optical properties; Thin films Registration No. 21561

Study of the p\vec{d}→n{pp}s charge-exchange reaction using a polarised deuterium target
Gou, B.; Mchedlishvili, D.; Bagdasarian, Z.; Barsov, S.; Garbonell, J.; Chiladze, D.; Dymov, S.; Engels, R.; Gaisser, M.; Gebel, R.; Grigoryev, K.; Hartmann, M.; Kacharava, A.; Khoukaz, A.; Kulessa, P.; Kulikov, A.; Lehrach, A.; Li, Z.; Lomidze, N.; Lorentz, B.; Macharashvili, G.; Merzliakov, S.; Mielke, M.; Mikirtychyants, M.; Mikirtychyants, S.; Nioradze, M.; Ohm, H.; Prasuhn, D.; Rathmann, F.; Serdyuk, V.; Shmakova, V.; Ströher, H.; Tabidze, M.; Trusov, S.; Tsirkov, D.; Uzikov, Y.; Valdau, Yu.; Wang, T.; Weidemann, C.; Wilkin, C.; Yuan, X.
Abstract: The vector and tensor analysing powers, Ayand Ayy, of the p d→n{pp}scharge-exchange reaction have been measured at a beam energy of 600MeV at the COSY-ANKE facility by using an unpolarised proton beam incident on an internal storage cell target filled with polarised deuterium gas. The low energy recoiling protons were measured in a pair of silicon tracking telescopes placed on either side of the target. Putting a cut of 3MeV on the diproton excitation energy ensured that the two protons were dominantly in the 1S0state, here denoted by {pp}s. The polarisation of the deuterium gas was established through measurements in parallel of proton–deuteron elastic scattering. By analysing events where both protons entered the same telescope, the charge-exchange reaction was measured for momentum transfers q ≥160MeV/c. These data provide a good continuation of the earlier results at q ≤140MeV/cobtained with a polarised deuteron beam. They are also consistent with impulse approximation predictions with little sign evident for any modifications due to multiple scatterings. These successful results confirm that the ANKE deuteron charge-exchange programme can be extended to much higher energies with a polarised deuterium target than can be achieved with a polarised deuteron beam. Registration No. 21560

Subthreshold Xi- Production in Collisions of p(3.5 GeV)+Nb
Agakishiev, G.; Arnold, O.; Balanda, A.; Belver, D.; Belyaev, A. V.; Berger-Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Chernenko, S.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O. V.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Göbel, K.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kornakov, G.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Yu. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, V.; Wagner, T.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y. V.
Abstract: Results on the production of the double-strange cascade hyperon Ξ are reported for collisions of p(3.5 GeV+Nb, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18 at GSI Helmholtzzentrum for Heavy-Ion Research, Darmstadt. For the first time, subthreshold Ξ production is observed in proton-nucleus interactions. Assuming a Ξ phase-space distribution similar to that of Λ hyperons, the production probability amounts to PΞ−=(2.0±0.4(stat)±0.3(norm)±0.6(syst))×10−4 resulting in a Ξ/(Λ+Σ0) ratio of PΞ−/ PΛ+Σ0=(1.2±0.3(stat)±0.4(syst))×10−2. Available model predictions are significantly lower than the estimated Ξ yield. Registration No. 21556

(V,Nb):TiO2 - a transparent conductor and ferromagnetic semiconductor !?
Cornelius, S.
Abstract: Both the property combinations a) transparent conductivity and b) diluted magnetic semiconductivity are based on the concept of dispersed substitutional doping of a suitable semiconductor with dopants that provide free electrons and/or carry a magnetic moment. The implications of current point defect theory with respect to defect formation enthalpies in anatase TiO2 are discussed in context with experimental results on electrical, optical and magnetic properties of V and Nb doped TiO2 thin films prepared by reactive magnetron sputtering. While transparent conductivity could be achieved via Nb doping, V doped films remain paramagnetic (in contrast to theoretical predictions).
Keywords: anatase, titanium oxide, magnetron sputtering, transparent conductive oxide, doping, magnetic semiconductor
  • Lecture (Conference)
    Deti.2 project meeting, 22.10.2014, Dresden, Deutschland
Registration No. 21553

Dopant activation and charge transport limits in transparent conductive (Al,Ga):ZnO and Nb:TiO2
Cornelius, S.
Abstract: Transparent conductive oxides (TCOs) are a class of wide bandgap metal oxides in which high densities of free charge carriers can be induced in such a way, that a unique combination of high optical transmittance in the visible spectral range and metal-like electrical conductivity is achieved. The influence of the oxygen partial pressure, substrate temperature, dopant concentration and substrate type on the properties (Al,Ga) doped ZnO and Nb doped TiO2 thin films has been studied systematically. The correlations between electrical, structural and optical properties as well as the elemental composition of the films have been characterized by a combination of Hall-effect, XRD, spectroscopic ellipsometry, spectral photometry, RBS and PIXE techniques including complementary XANES and TEM studies. The results are discussed with a focus on understanding the dopant incorporation into the ZnO and TiO2 host materials as well as finding physical limits for the resistivity based on charge transport models for degenerate polar semiconductors.
Keywords: transparent conductive oxide, zinc oxide, doping, titanium oxide, anatase, electron mobility, reactive sputtering, magnetron sputtering
  • Invited lecture (Conferences)
    Institutsseminar, Institut für experimentelle Physik II, Universität Leipzig, 26.11.2014, Leipzig, Deutschland
Registration No. 21552

Formation and propagation of laser-driven plasma jets in an ambient medium studied with X-ray radiography and optical diagnostics
Diziere, A.; Pelka, A.; Ravasio, A.; Loupias, B.; Falize, E.; Kuramitsu, Y.; Sakawa, Y.; Morita, T.; Pikuz, S.; Yurchak, R.; Koenig, M.
Abstract: In this paper, we present experimental results obtained on the LULI2000 laser facility regarding structure and dynamics of astrophysical jets propagating in interstellar medium. The jets, generated by using a cone-shaped target, propagate in a nitrogen gas that mimics the interstellar medium. X-ray radiography as well as optical diagnostics were used to probe both high and low density regions. In this paper, we show how collimation of the jets evolves with the gas density. Registration No. 21551

Investigation of ionoluminescence of semiconductor materials using helium ion microscopy
Veligura, V.; Hlawacek, G.; van Gastel, R.; Zandvliet, H. J. W.; Poelsema, B.
Abstract: Helium ion microscopy has been employed to investigate the ionoluminescence of various semiconduc- tors. We have verified the possibility of application of this technique for high-resolution ionolumines- cence analysis of this kind of materials. In this work the ionoluminescence signal was induced by a sub- nanometer Heþ beam with an energy of 35 keV. Several types of semiconductor samples were investigated: bulk materials, nanowires and quantum dots. All samples were found to exhibit ionoluminescence. However, the ionoluminescence signal rapidly degrades under the ion irradiation. The signal degradation was found to depend not only on the sample's composition, but also on its size. The ionoluminescence emission spectra were recorded and emission peaks identified.
Keywords: Ionoluminescence Helium ion microscopy Semiconductors Nanowires Quatum dots Registration No. 21549

Ion irradiation and nanoindentation as a screening test for irradiation effects on neutron-irradiated ferritic/martensitic high-Cr steels
Heintze, C.; Akhmadaliev, S.; Altstadt, E.; Bergner, F.
Abstract: A combined approach based on ion irradiation and nanoindentation as a screening test procedure for the irradiation response of structural materials foreseen for components exposed to heavy neutron irradiation has been selected and specified in detail. Important constituents of the approach are:
• Design of the ion irradiation experiments using the MD code SRIM and taking into account recommendations according to [1], detailed documentation of the irradiation experiments and the SRIM calculations,
• Nanoindentation testing over a large range of indentation depths (from about 5% to 100% of the thickness of the ion-irradiated layer) to gain information on the indentation size effect and the substrate effect, analysis according to the Oliver-Pharr method [2,3],
• Elimination of the indentation size effect (ISE) based on an unirradiated reference sample of the same material using a suitable model (e.g. [4]), elimination of the substrate effect.

A version of the approach specified above was applied to unirradiated, ion-irradiated and neutron-irradiated 9%Cr F/M steel T91 (MATTER reference material). The findings indicate that the approach based on ion irradiation and nanoindentation is suitable as a screening test for F/M steels exposed to neutron irradiation.

References
[1] R. E. Stoller, M. B. Toloczko, G. S. Was, A. G. Certain, S. Dwaraknath, F. A. Garner, Nucl. Instrum. Methods Phys. Res. B 310 (2013) 75–80.
[2] W. C. Oliver, G. M. Pharr, J. Mater. Res., 7 (1992) 1564–1583.
[3] W. C. Oliver, G. M. Pharr, J. Mater. Res., 19 (2004) 3–20.
[4] W. D. Nix, H. Gao, J. Mech. Phys. Solids, 46 (1998) 411–425.

Keywords: ion irradiation, neutron irradiation, nanoindentation, irradiation hardening, ferritic/martensitic steels, T91
  • Lecture (Conference)
    MATTER - “MATerials TEsting and Rules“ Project Final Workshop, 20.-22.10.2014, Rom, Italy
Registration No. 21544

The Zn-vacancy related green luminescence and donor-acceptor pair emission in ZnO grown by pulsed laser deposition
Wang, Z.; Su, S. C.; Younas, M.; Ling, F. C. C.; Anwand, W.; Wagner, A.
Abstract: Low temperature (10 K) photoluminescence study shows that green luminescence (GL) peaked at 2.47 eV and near band edge (NBE) emission at 3.23 eV are introduced in undopd ZnO grown by pulsed laser deposition (PLD) after the 900°C annealing. The NBE emission exhibiting blue shift with increasing temperature is assigned to the transitions of donor-acceptor-pair (DAP)/free-electron-to-acceptor (FA). Positron annihilation spectroscopy (PAS) study shows that the introduction of the GL is correlated with the formation of the Zn vacancy-related defect (VZn). Comparing the transition energies of VZn obtained by the previous first principle calculation [Janotti and Van de Walle, Phys. Rev. B 76, 165202 (2007)], the GL is associated with the transition from the conduction band to the ε(-/2-) state of VZn and the DAP/FA emission involves the acceptor level ε(0/-) of VZn.
Keywords: ZnO, green luminescence, Zn vacancy, Registration No. 21543

Influence of the discharge regime on Ti thin films growth and properties in dc, single pulsed and chopped high power impulse magnetron sputtering
Meško, M.; Heller, R.; Hübner, R.; Krause, M.
Abstract: High power impulse magnetron sputtering (HiPIMS) has been becoming an appealing deposition process for synthesis of high quality coatings over the last decade. It utilizes average power similar to the dc magnetron sputtering (DCMS) applied on magnetron target, which is however concentrated in short pulses. This ensures generation of dense plasmas with high fraction of ionized film forming species. Control over the energy and trajectory of ionized sputtered species can lead to the formation of coatings with improved properties. Despite of certain advantages the HiPIMS process has often a lower deposition rate compared to DCMS. This is one reason which hinders the HiPIMS process from further exploration in industrial applications. However more recently it has been shown that deposition rates of Ti thin films can be significantly increased by so called chopped-HiPIMS (c-HiPIMS) technique [1]. In this case a single HiPIMS pulse is decomposed into several individual pulses with microsecond pulse off-times. C-HiPIMS can be especially effective in suppression of thermal spikes on the target. The effect of thermal spikes is most pronounced during long single HiPIMS pulses. It negatively influences mobility of arriving ad-atoms leading to the formation of larger grains and rougher surface of Ti thin films [2]. In present work we compare the density, crystallinity, roughness, and microstructure of Ti thin films prepared by dc, single pulsed, and c-HiPIMS. Much attention has been paid on role of microsecond pulse off-times on Ti thin films properties. Plasma parameters have been measured to supplement our investigations.
References:
[1] P. M. Barker, E. Lewin, and J. Patscheider “Modified high power impulse magnetron sputtering process for increased deposition rate of titanium” J. Vac. Sci. Technol. A 31 (2013) 0606041
[2] F. J. Jing, T. L. Yin, K. Yukimura, H. Sun, Y. X. Leng, and N. Huang “Titanium film deposition by high-power impulse magnetron sputtering: Influence of pulse duration” Vacuum 86 (2012) 2114

Keywords: HiPIMS, Ti thin film, microstructure, plasma parameters
  • Poster
    14th International Conference on Plasma Surface Engineering, 15.-19.09.2014, Garmisch-Partenkirchen, Deutschland
Registration No. 21542

The effect of He on irradiation hardening of Fe-9Cr-based non-ODS and ODS alloys at 300°C
Heintze, C.; Kögler, R.; Bergner, F.; Hernández Mayoral, M.
Abstract: The influence of helium on the irradiation hardening and embrittlement of reduced-activation ferritic/martensitic Cr-steels and their oxide dispersion strengthened variants under fusion-relevant irradiation conditions is still a concern. While the fact that He can influence the mechanical properties is well established [1,2], the underlying mechanisms are not fully understood [1,2]. In this work the effect of He and displacements per atom (dpa) on the irradiation-induced hardening of an Fe-9at%Cr alloy, Eurofer97 and an oxide dispersion strengthened variant of Eurofer (ODS-Eurofer) at 300°C was studied. Self-ion irradiation was applied to simulate the neutron-irradiation-induced damage. To separate the effect of helium different irradiation modes were applied. Apart from single-beam irradiations with He or self-ions, only, Helium was implanted prior to (pre-implantation), simultaneously (dual-beam irradiation) or following the (post-implantation) self-ion irradiation. The ion irradiated layer was characterized by means of nanoindentation. We conclude, that:
• there is a significant interaction between dpa and He
• pre-implantation of He followed by self-ion irradiation is not suitable to replace simultaneous irradiations or to simulate neutron irradiation induced damage
• nano-oxides in ODS-Eurofer mitigate the effect of helium on irradiation hardening

[1] H. Trinkaus, B.N. Singh, J. Nucl. Mater. 323 (2003) 229
[2] R. Schäublin, Y.L. Chiu, J. Nucl. Mater. 362 (2007) 152

Keywords: irradiation hardening, ODS, dual-beam, ion irradiation, nanoindentation
  • Poster
    2nd International Workshop on ODS Materials, 26.-27.06.2014, Dresden, Deutschland
Registration No. 21541

Using nature's genius for pollutant detection
Raff, J.; Weinert, U.; Nikolaus, N.; Guenther, T.; Strehlitz, B.; Pollmann, K.
Abstract: In all environments single cell organisms such as bacteria are directly affected by changing and sometimes extreme environmental conditions. This includes not only pH, temperature and salinity but also the presence of toxic ions, compounds and complexes. It is thusly essential for these microorganisms to possess a robust and selectively permeable cell surface. For this purpose, many bacteria form a proteinaceous cell envelope, the so called surface layer (S-layer). This cell envelope has different functions in different organisms for example the binding of toxic metals and metalloids to protect cells from being damaged by these elements. On other cells, S-layers may act as immobilization matrix for exoenzymes, as molecular sieve or as ion and molecule trap or they protect the cell from being affected by other bacteria or by lytic enzymes. S-layers are composed of identical protein or glycoprotein monomers, which are able to self-assemble to highly ordered monomolecular layers. They form para-crystalline sheets in suspension, on interfaces and on surfaces. Furthermore, on the surface of such a layer different functional groups are available which can be modified without the loss of its structure. The protein layers are in general mechanically and chemically highly stable. These properties make S-layers very interesting building blocks for the construction of new bioinspired nanomaterials and nanocoatings. Using the two-dimensional protein arrays in combination with layer-by-layer technique different kinds of technical surfaces can be functionalized.
This technique is used to design a new kind of sensory layers which will allow detecting small amounts of analytes with high selectivity. This sensory device will consist of an S-layer coating, a selective receptor and two fluorescence dyes. Aptamers were used as compound specific receptors . These are short, single stranded nucleic acid oligomers that meet the requirements for a more selective and sensitive detection of pollutants in nature, medicine and industry. Aptamers are able to recognize almost all classes of substrates and bind them in analogy to antigen-antibody interactions. By using an in vitro selection and amplification technique aptamers can be developed for pollutants like heavy metals, pharmaceuticals but also for proteins and complex targets like viruses and microbial spores. Currently, several aptamers for different antibiotics have been selected and experiments confirmed their high selectivity for single antibiotics or groups of antibiotics. As third component two fluorescence dyes allowing a FRET as signal transducer system will be coupled onto the S-layer lattice. This setup can be combined in different ways to optimize the sensitivity and selectivity of the sensor. Comparable to the binding of exoenzymes on S-layer carrying cells the three sensor components can also be linked to S-layer coated technical surfaces. In first experiments we coupled the model aptamer, anti-thrombin-aptamer, on S-layer proteins and proved its functionality after being linked to the protein. Furthermore, we modified S-layer proteins with a FRET pair and proved the energy transfer between them. We used a FRET pair containing a green and red fluorescence dye and succeed to detect a FRET between the S-layer linked fluorescence dyes. The FRET efficiency was 40 %. Because of the regular arranged functional groups on the S-layer lattice, coupling of the sensor components can be done in a defined and reproducible way.
In further work we will combine all components, aptamers and fluorescence dyes, on the S layer proteins. The aptamer will bind the specific analyte, affecting also the fluorescence dyes and disturbing FRET because of their close proximity to each other. In result a sensory layer is developed which uses the high specificity of aptamers and fluorescence dyes for an easy detection due to an optical signal. Additionally, in the future other techniques such as phage surface display will be used to select also peptide based binding molecules. Hopefully, this will allow detecting even more and also other kinds of pollutants not being bound by aptamers.

Keywords: S-layer, aptamer, biosensor, FRET
  • Invited lecture (Conferences)
    Rapid Methods Europe 2014, 03.03.-02.04.2014, Noordwijkerhout, Niederland
Registration No. 21540

Transport in mesoscopic conductors
Erbe, A.
Abstract: Electronic transport in mesoscopic structures

The size of electrical components has been scaled down by several orders of magnitude during the past decades arriving at structure sizes of only tens of nanometers in modern circuits. Electrical current on the nanocale obeys different laws than in macroscopic conductors. The resistance of macroscopic conductors is described by Ohm’s law, assuming diffusive charge transport carried by the conduction electrons. At small length scales this concept cannot be applied any more, electrons move ballistically at these length scales and transport needs to be described using a scattering approach. We will review the concepts used to describe mesoscopic conductors and give examples for typical structures that can be treated using these concepts.

Molecular electronics

The use of single molecules as active elements in electrical circuits may serve as alternative technology for building integrated circuits on the nanoscale. In this presentation we want to give an overview on various techniques that have been used successfully to contact single molecules and to characterize them electrically. Especially the comparison between different techniques shows that a single measurement is always prone to artifacts originating from the unknown microscopic details of the junctions. It is therefore necessary to perform a statistically relevant number of measurements in order to resolve molecular properties. Using these techniques various properties of the molecules can be studied. Special examples are the influence of conformational changes of the molecules, differences between various coupling endgroups of the molecules, effects of light-irradiation onto the molecular junctions, and the influence of self-organization in DNA nanostructures.
  • Invited lecture (Conferences)
    PIER summer school, 06.-09.10.2014, Hamburg, Deutschland
Registration No. 21539

Introduction to transport in confined geometries an across point contacts
Erbe, A.
Abstract: The size of electrical components has been scaled down by several orders of magnitude during the past decades arriving at structure sizes of only tens of nanometers in modern circuits. Electrical current on the nanocale obeys different laws than in macroscopic conductors. The resistance of macroscopic conductors is described by Ohm’s law, assuming diffusive charge transport carried by the conduction electrons. At small length scales this concept cannot be applied any more, electrons move ballistically at these length scales and transport needs to be described using a scattering approach. We will review the concepts used to describe mesoscopic conductors and give examples for typical structures that can be treated using these concepts.
Mechanically controllable breakjunctions (MCBJs) are excellent tools to form stable metallic contacts consisting of single atoms, only. In these devices, a tiny metallic bridge is broken by mechanically bending the underlying substrate. During the breaking, the number of atoms taking part in the conduction is reduced gradually, leading to a step-wise decrease of the conductance of the whole junction. This behavior is understood by taking the atomic orbitals, which contribute to the conductance mechanism, into account1. We will show how the experimental results showing this behavior can be obtained and compared to theoretical predictions. Apart from being a fascinating model system for mesoscopic conductance, MCBJs can be used for making contacts to other nanoscale conductors, such as single molecules. We will give a brief introduction on the transport mechanisms involved in single molecule conductance and show measurements of such systems using MCBJs2.

1. Scheer, E. et al. The signature of chemical valence in the electrical conduction through a single-atom contact. Nature 394, 154–157 (1998).
2. Zotti, L. A. et al. Revealing the Role of Anchoring Groups in the Electrical Conduction Through Single-Molecule Junctions. Small 6, 1529–1535 (2010).
  • Invited lecture (Conferences)
    MAINZ summer school, 25.-29.08.2014, Mainz, Deutschland
Registration No. 21538

Development of a Compton Camera for online ion beam range verification via prompt gamma detection
Aldawood, S.; Böhmer, M.; Bortfeldt, J.; Castelhano, I.; Dedes, G.; Lutter, R.; Gernhäuser, R.; Kolff, H. Von D.; Lang, C.; Maier, L.; Petzoldt, J.; Römer, K.; Pausch, G.; Fiedler, F.; Schaart, D. R.; Parodi, K.; Thirolf, Peter G.; Auer, M.
Abstract: Precise and preferably online ion beam range verification is a mandatory prerequisite to fully exploit the advantages of hadron therapy in cancer treatment. Our aim is to develop an imaging system based on a Compton camera designed to detect prompt gamma-rays induced by nuclear reactions between the ion beam and biological tissue. The Compton camera prototype consists of a stack of six customized double-sided Si-strip detectors (DSSSD, 50x50 mm2,128 strips/side) acting as scatterer, while the absorber is formed by a monolithic LaBr3:Ce scintillator crystal (50x50x30mm3) read out by a position-sensitive multi-anode photomultiplier (Hamamatsu H9500). This camera has the ability to not only detect the scattered photon, but it can also track the scattered Compton electron due to the way of designing and arranging the scatter detectors, and the multi-MeV energy of the incidentprompt gamma-rays[1].Thereflectively wrapped LaBr3:Ce detector was characterized with calibration sources, showing an excellent performance of this crystal. The time resolution was determined to be 273ps and the relative energy resolution at 662 keV was found to be 3.8%.The study of the DSSSD detectors together with the full Compton camera properties are inprogress both in the laboratory as well as at the online facilities.

References
[1] C. Lang et al., Journal of Instrumentation 9 (2014) P01008.
This work is supported by the DFG Cluster of Excellence MAP (Munich-Centre for Advanced Photonics)

Keywords: Compton Camera, range verification, particle therapy
  • Poster
    International Workshop on Range Assessment and Dose Verification in Particle Therapy, 29.-30.09.2014, Dresden, Germany
Registration No. 21536

Entwicklung von Elektromagneten mit kurzen, hohen Strompulsen für die laserbasierte Protonentherapie
Schürer, M.; Herrmannsdörfer, T.; Karsch, L.; Kroll, F.; Masood, U.; Sobiella, M.; Pawelke, J.
  • Poster
    5. Dresdner Medizintechnik Symposium, 01.-03.12.2014, Dresden, Deutschland
  • Contribution to proceedings
    5. Dresdner Medizintechnik Symposium, 01.-03.12.2014, Dresden, Deutschland
    A. Förster, J. Füssel, M. Gelinsky, E. Koch, H. Malberg, W. Vonau (Hrsg.): Biomedizinische Technik – Von der Grundlagenforschung zum Transfer. Reports on Biomedical Engineering, Stuttgart: Steinbeis-Edition, ISBN 978-3-95663-018-7, 94
Registration No. 21535

Turbulent amplification of magnetic fields in laboratory laser-produced shock waves
Meinecke, J.; Doyle, H. W.; Miniati, F.; Bell, A. R.; Bingham, R.; Crowston, R.; Drake, R. P.; Fatenejad, M.; Koenig, M.; Kuramitsu, Y.; Kuranz, C. C.; Lamb, D. Q.; Lee, D.; Macdonald, M. J.; Murphy, C. D.; Park, H-S.; Pelka, A.; Ravasio, A.; Sakawa, Y.; Schekochihin, A. A.; Scopatz, A.; Tzeferacos, P.; Wan, W. C.; Woolsey, N. C.; Yurchak, R.; Reville, B.; Gregori, G.
Abstract: X-ray and radio observations of the supernova remnant Cassiopeia A reveal the presence of magnetic fields about 100 times stronger than those in the surrounding interstellar medium. Field coincident with the outer shock probably arises through a nonlinear feedback process involving cosmic rays. The origin of the large magnetic field in the interior of the remnant is less clear but it is presumably stretched and amplified by turbulent motions. Turbulence may be generated by hydrodynamic instability at the contact discontinuity between the supernova ejecta and the circumstellar gas9. However, optical observations of Cassiopeia A indicate that the ejecta are interacting with a highly inhomogeneous, dense circumstellar butt bank formed before the supernova explosion. Here we investigate the possibility that turbulent amplification is induced when the outer shock overtakes dense clumps in the ambient medium. We report laboratory experiments that indicate the magnetic field is amplified when the shock interacts with a plastic grid. We show that our experimental results can explain the observed synchrotron emission in the interior of the remnant. The experiment also provides a laboratory example of magnetic field amplification by turbulence in plasmas, a physical process thought to occur in many astrophysical phenomena. Registration No. 21534

Experimental demonstration of an inertial collimation mechanism in nested outflows
Yurchak, R.; Ravasio, A.; Pelka, A.; Pikuz, S.; Falize, E.; Vinci, T.; Koenig, M.; Loupias, B.; Benuzzi-Mounaix, A.; Fatenejad, M.; Tzeferacos, P.; Lamb, D. Q.; Blackman, E. G.
Abstract: Interaction between a central outflow and a surrounding wind is common in astrophysical sources powered by accretion. Understanding how the interaction might help to collimate the inner central outflow is of interest for assessing astrophysical jet formation paradigms. In this context, we studied the interaction between two nested supersonic plasma flows generated by focusing a long-pulse high-energy laser beam onto a solid target. A nested geometry was created by shaping the energy distribution at the focal spot with a dedicated phase plate. Optical and x-ray diagnostics were used to study the interacting flows. Experimental results and numerical hydrodynamic simulations indeed show the formation of strongly collimated jets. Our work experimentally confirms the “shock-focused inertial confinement” mechanism proposed in previous theoretical astrophysics investigations. Registration No. 21533

Realizing a reference setup for irradiation experiments with laser-accelerated proton pulses (at the Draco laser)
Obst, L.; Zeil, K.; Metzkes, J.; Kraft, S.; Schramm, U.
Abstract: By focusing an ultra-short high-intensity laser pulse on a solid target, pulses of protons and other positively charged ions with energies of several 10 MeV per nucleon are generated. The properties of these particle beams such as their energy and absolute number are highly dependent on experimental conditions like laser and target parameters. In order to achieve principal comparability between different experimental campaigns at the Draco laser system at the Helmholtz-Zentrum Dresden-Rossendorf, a reference setup for the laser ion acceleration experiment was established. A configuration is sought in which proton beams of reproducible characteristics are generated. To ensure a high stability of the proton spectra, the application of longer focal length parabolas (f ~ 1000 mm) will be tested for this setup, according preparatory studies being presented in this talk.
Keywords: accelerators, laser-driven proton acceleration, high-intensity lasers, beams and electromagnetism
  • Lecture (Conference)
    DPG-Tagung 2014, 17.-21.03.2014, Berlin, Deutschland
Registration No. 21531

Laserbasierte Teilchenbeschleunigung und deren Anwendung in der Strahlentherapie
Pawelke, J.
  • Invited lecture (Conferences)
    Referententagung des Strahlenschutzseminar in Thüringen e.V., 15.-16.03.2013, Heyda, Deutschland
Registration No. 21529

Concept of a compact gantry for laser based proton therapy.
Karsch, L.; Bussmann, M.; Enghardt, W.; Kroll, F. Lorian; Masood, U.; Pawelke, J.
  • Poster
    52th Particle Therapy Cooperative Group (PTCOG) Meeting, 02.-08.06.2013, Essen, Deutschland
  • Contribution to proceedings
    52th Particle Therapy Cooperative Group (PTCOG) Meeting, 02.-08.06.2013, Essen, Deutschland
    Proceedings of the 52th Particle Therapy Cooperative Group (PTCOG) Meeting, 312
Registration No. 21528

Einfluss der Pulslänge auf die Sättigungskorrektur von Ionisationskammern in gepulsten Strahlungsfeldern.
Gotz, M.; Karsch, L.; Pawelke, J.
  • Lecture (Conference)
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 18.-21.09.2013, Köln, Deutschland
  • Contribution to proceedings
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 18.-21.09.2013, Köln, Deutschland
    H. Treuer (Ed.): Medizinische Physik 2013, Deutsche Gesellschaft für Medizinische Physik e. V., ISBN 978-3-9816002-1-6, 318-321
Registration No. 21527

Optimierung der Bestrahlungsplanungsstrategie für laserbeschleunigte Protonen.
Findeisen, A.; Karsch, L.; Masood, U.; Pawelke, J.
  • Poster
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 18.-21.09.2013, Köln, Deutschland
  • Contribution to proceedings
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 18.-21.09.2013, Köln, Deutschland
    H. Treuer (Ed.): Medizinische Physik 2013, Deutsche Gesellschaft für Medizinische Physik e. V., ISBN 978-3-9816002-1-6, 714-715
Registration No. 21526

Proton therapy in Dresden: present and future
Pawelke, J.
  • Invited lecture (Conferences)
    International Conference on the Future of Radiation Oncology: Imaging, Dosimetry, Biology and Therapy (7th Berder Workshop), 25.-28.09.2013, Berder Island, France
Registration No. 21525

Review on radiobiological studies using laser driven particle beams:From in vitro experiments to human tumor irradiations on mice
Pawelke, J.
  • Invited lecture (Conferences)
    International Workshop on Microbeam Probes of Cellular Radiation Response (11th Microbeam Workshop), 03.-04.10.2013, Bordeaux, Frankreich
Registration No. 21524

Development of a compact particle therapy facility with laser- driven ion beams via novel pulse powered gantry systems
Masood, U.; Bussmann, M.; Baumann, M.; Cowan, T. E.; Enghardt, W.; Herrmannsdörfer, T.; Hofmann, K. M.; Kaluza, M.; Karsch, L.; Kroll, F.; Schramm, U.; Schürer, M.; Wilkens, J. J.; Pawelke, J.
  • Contribution to proceedings
    Joint Conference in Medical Physics, 07.-10.09.2014, Zürich, Schweiz
    Proceedings of the Joint Conference in Medical Physics, 27-28
  • Lecture (Conference)
    Joint Conference in Medical Physics, 07.-10.09.2014, Zürich, Schweiz
Registration No. 21523

A treatment planning study to assess the feasibility and the limitations of laser-driven proton therapy
Hofmann, K. M.; Masood, U.; Pawelke, J.; Wilkens, J. J.
  • Contribution to proceedings
    Joint Conference in Medical Physics, 07.-10.09.2014, Zürich, Schweiz
    Proceedings of the Joint Conference in Medical Physics, 29
  • Lecture (Conference)
    Joint Conference in Medical Physics, 07.-10.09.2014, Zürich, Schweiz
Registration No. 21522

Wechselwirkung langsamer hochgeladener Ionen mit Ionenkristalloberflächen und ultradünnen Kohlenstoffmembranen
Wilhelm, R. A.
Abstract: In der vorliegenden Arbeit wurde die Strukturbildung durch Einzeleinschlag von langsamen hochgeladenen Ionen (v < 5·10^5 m/s, Q < 40) auf Ionenkristalloberflächen und freistehenden amorphen Kohlenstofffolien untersucht. Mittels experimenteller Methoden der Rasterkraft-, Transmissionselektronen- und Heliumionenmikroskopie wurden die in jüngster Zeit gewonnenen Modellbeschreibungen für Nanostrukturbildung an Oberflächen erweitert. Beim Auftreffen eines langsamen hochgeladenen Ions auf die (001)-Oberfläche von KCl können Nanostrukturen mit Ausdehnungen bis zu einigen 10nm entstehen. Die damit verknüpften Desorptionsausbeuten von bis zu 3000 Atomen pro Ion aus der Oberfläche werden vor allem durch die Deposition der potentiellen Energie in sehr oberflächennahe Schichten erklärt. Die kinetische Energie der Ionen wirkt jedoch unterstützend auf die Entstehung und Vergrößerung der Lochstrukturen. Die Entstehung der Strukturen durch die potentielle Energie kann konsistent im Bild der defektinduzierten Desorption erklärt werden.
Für die CaF2(111)-Oberfläche konnte gezeigt werden, dass auch unter ununterbrochenen Ultrahochvakuumbedingungen Nanohügel durch Ionenbeschuss erzeugt werden können. Die Größenverteilung beobachteter Nanohügel ist dabei jedoch um einen Faktor 3 kleiner im Vergleich zu atmosphärenexponierten Proben. Der Einfluss der Atmosphäre auf die beobachteten Strukturgrößen wird diskutiert. Für niedrigere Ladungszustände als nötig für Nanohügelerzeugung wurden ioneninduzierte Kristalldefekte durch nasschemisches Ätzen der Oberfläche nachgewiesen. Diese Tatsache verbindet die Beschreibung der Strukturbildung durch elektronische Anregungen in Alkali- und Erdalkalihaliden.
Für den Durchgang von hochgeladenen Ionen durch 1 nm dicke, freistehende und amorphe Kohlenstofffolien zeigte sich, dass Poren durch Einzelioneneinschlag entstehen, sobald ein Schwellwert von etwa Q = 25 in der Ionenladung überschritten wurde. Erstmalig konnte gezeigt werden, dass sich bei der Transmission der Ionen zwei unterschiedliche Ladungszustandsverteilungen bilden. Die Ausbildung der beiden Verteilungen wird durch einen stark stoßparameterabhängigen Ladungsaustausch beschrieben. Neben dem Einfluss der potentiellen Energie bei der Porenbildung ist auch der Einfluss der kinetischen Energie untersucht worden. Um den Anteil nuklearer und elektronischer kinetischer Energieverluste in Abhängigkeit des Ionenladungszustandes abzuschätzen, wurde ein Modell im Rahmen der Beschreibung statistischer Atome bzw. Ionen aufgestellt. Auf Basis dieses Modells wird der Einfluss der kinetischen Energiedeposition und die damit verbunde- ne Synergie aus potentieller und kinetischer Energie bei der Strukturbildung diskutiert.

The formation of nano-structures due to the impact of individual slow highly charged ions (v < 5 · 105 m/s, Q < 40) on surfaces of ionic crystals and 1 nm thick, freestanding and amorphous carbon membranes is investigated in this work. By an experimental approach using atomic force, transmission elec- tron and helium ion microscopy recent model descriptions for the formation processes of highly charged ion induced nano-structures are expanded. Upon impact of slow highly charged ions on the (001)-surface of KCl pit-like structures with sizes up to a few 10nm are found. The corresponding desorption yields of a few thousand atoms per ion are mainly attributed to the deposition of potential energy in a shallow region near the surface. The kinetic energy has only a minor effect on the formation processes. The structure formation due to potential energy deposition is described consis- tently in the framework of a defect induced desorption model.
For the CaF2(111) surface it is shown, that even without breaking the vac- uum between irradiation and analyses ion induced nano-hillocks are present. However, the sizes of the nano-hillocks are about a factor of 3 smaller than the sizes after exposure to atmosphere. The influence of the atmosphere conditions on the structure sizes is discussed. For lower charge states than needed for nano-hillock formation ion-induced defects are revealed by wet- chemical etching of the exposed surfaces. The existence of defects for lower charge states combines the model descriptions of nano-structure formation by strong electronic excitations for alkali and earth-alkali halide surfaces. Pore formation due to highly charged ion impact on 1 nm thick, freestanding and amorphous carbon films is observed for ions with a charge state above a threshold of about Q = 25. It has been shown for the first time that two distinct exit charge state distributions are formed upon transmission of the ions through the membrane. The formation of the distributions is explained
by a strongly impact parameter dependent charge exchange. Besides the influence of the potential energy on the pore formation also the importance of the kinetic energy is investigated. To distinguish between nuclear and electronic losses in the case of highly charged ions at low velocities a model for charge state dependent energy loss is proposed. Based on the descrip- tion of statistical atoms and ions, respectively, the synergy of potential and kinetic energy upon nano-structure formation is discussed.
  • Doctoral thesis
    TU Dresden, 2014
    Mentor: Prof. Jürgen Fassbender / Dr. Stefan Facsko
    149 Seiten
Registration No. 21521

In vivo dose response to laser driven electron beams
Oppelt, M.; Baumann, M.; Bergmann, R.; Beyreuther, E.; Brüchner, K.; Hartmann, J.; Kaluza, M.; Karsch, L.; Krause, M.; Laschinsky, L.; Lessmann, E.; Nicolai, M.; Reuter, M.; Sävert, A.; Schnell, M.; Schürer, M.; Pawelke, J.
  • Contribution to proceedings
    Joint Conference in Medical Physics, 07.-10.09.2014, Zürich, Schweiz
    Proceedings of the Joint Conference in Medical Physics, 191
  • Lecture (Conference)
    Joint Conference in Medical Physics, 07.-10.09.2014, Zürich, Schweiz
Registration No. 21520

Laserbasierte Partikeltherapie.
Pawelke, J.
Abstract: Laserbasierte Partikeltherapie.
  • Invited lecture (Conferences)
    Symposium “Innovationen in der Radioonkologie”, 24.09.2014, Dresden, Deutschland
Registration No. 21519

Development of short-pulsed high-field electromagnetic dipoles for laser-based proton therapy
Schürer, M.; Herrmannsdörfer, T.; Karsch, L.; Kroll, F.; Masood, U.; Pawelke, J.
Abstract: Introduction
During the last years, the new technology of laser based particle acceleration was developed at such a rate that medical application for cancer therapy becomes conceivable. Promising more compact and economic accelerators, the laser technology however generates intense ultra-short (~ ps) pulsed proton beams with large divergence and broad energy spectrum. Within the German joint research project “onCOOPtics” the clinical applicability of such pulsed proton beams is investigated including the development of a laser accelerator and a suitable beam transport.
Methods
A compact beam transport system was designed enabling an efficient transport of proton pulses from generation to treatment site. The initially divergent proton beam is captured by a cylindrical electromagnet (solenoid), deflected by 45° dipole magnets and formed by quadrupole magnets, whereas the spectrum is shaped by adaptable lead apertures. For realization, electromagnetic dipoles with magnetic fields of up to 10 T are required to deflect up to 220 MeV protons. These field strengths are achieved by in-house developed non-ferrous dipoles that consist of 80 copper coils in 12 layers and are operated at peak currents of up to 20 kA. To handle the high currents and the generated heat the dipoles are externally cooled and operated in 1 ms short pulses synchronized with the laser repetition frequency.
Results
The prototype of a short-pulsed electromagnetic dipole magnet was designed and manufactured. Results of the experimental characterization and first performance tests at a conventional Tandem accelerator are under way.
Conclusion
Pulsed electromagnetic dipoles as crucial components of a compact beam line for laser-accelerated protons are engineered. Following validation of their suitability at a conventional accelerator the dipoles will be implemented and further tested at a laser accelerator. Together with improvement of the dipole the design of quadrupoles will start.
  • Abstract in refereed journal
    Biomedizinische Technik 59(2014)Suppl 1, 891
    DOI-Link: http://dx.doi.org/10.1515/bmt-2014-5011
  • Lecture (Conference)
    48. Jahrestagung der Deutschen Gesellschaft für Biomedizinische Technik, 08.-10.10.2014, Hannover, Deutschland
  • Poster
    48. Jahrestagung der Deutschen Gesellschaft für Biomedizinische Technik, Hannover, Germany, 8-10 Oct 2014, 08.-10.10.2014, Hannover, Deutschland
Registration No. 21518

Development of laser-driven proton beam therapy
Masood, U.; Bussmann, M.; Cowan, T.; Enghardt, W.; Herrmannsdörfer, T.; Kaluza, M.; Krause, M.; Pawelke, J.; Sauerbrey, R.; Schramm, U.; Baumann, M.
  • Abstract in refereed journal
    Annals of Oncology 25(2014)Suppl 4, iv546-iv547
    DOI-Link: http://dx.doi.org/10.1093/annonc/mdu358.3
  • Lecture (Conference)
    Congress of the European Society for Medical Oncology (ESMO) on “Precision Medicine in Cancer Care”, 26.-30.09.2014, Madrid, Spanien
  • Poster
    Congress of the European Society for Medical Oncology (ESMO) on “Precision Medicine in Cancer Care”, 26.-30.09.2014, Madrid, Spanien
Registration No. 21517

Comparison study of in vivo dose response to laser driven versus conventional electron beam.
Oppelt, M.; Baumann, M.; Begrmann, R.; Beyreuther, E.; Brüchner, K.; Hartmann, J.; Karsch, L.; Krause, M.; Laschinsky, L.; Leßmann, E.; Nicolai, M.; Reuter, M.; Richter, C.; Sävert, A.; Schürer, M.; Schnell, M.; Woithe, J.; Kaluza, M.; Pawelke, J. Registration No. 21515

Scaling of TNSA-accelerated proton beams with laser energy and focal spot size
Obst, L.; Zeil, K.; Metzkes, J.; Kraft, S.; Schramm, U.
Abstract: By focusing an ultra-short high-intensity laser pulse on a solid target, pulses of protons and other positively charged ions with energies of several 10 MeV per nucleon are generated. The properties of these particle beams such as their energy and absolute number are highly dependent on experimental conditions like laser and target parameters. In order to achieve principal comparability between different experimental campaigns at the Draco laser system at the Helmholtz-Zentrum Dresden-Rossendorf, a reference setup for the laser ion acceleration experiment was established. A configuration is sought in which proton beams of reproducible characteristics are generated. To ensure a high stability of the proton spectra, the application of longer focal length parabolas (f ~ 1000 mm) will be tested for this setup, according preparatory studies being presented in this paper.
Keywords: accelerators, laser-driven proton acceleration, high-intensity lasers, beams and electromagnetism
  • Contribution to proceedings
    IPAC'14 - 5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Deutschland
    IPAC2014 - Proceedings, TUPME033
  • Poster
    IPAC'14 - 5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Deutschland
Registration No. 21514

Energetic stability of solute–carbon–vacancy complexes in bcc iron
Bakaev, A.; Terentyev, D.; Zhurkin, E. E.; van Neck, D.
Abstract: The strong binding between a vacancy and carbon in bcc iron plays an important role in the evolution of radiation-induced microstructure. Our previous ab initio study points to the fact that the vacancy–carbon (V–C) pair can serve as a nucleus for the solute-rich clusters. Here, we continue the ab initio study by considering the interaction of mixed solute clusters (Mn, Ni and Si) with the V–C pair, and the interaction of typical alloying elements of Fe-based steels (i.e., Mn, Ni, Cu, Si, Cr and P) with di-carbon–vacancy pair (V–C2). We have identified the sequence of growth of Ni, Si and Mn solute-rich clusters nucleating on the V–C pair. The mixed-solute–V–C configurations are found to be less stable clusters than pure-solute–V–C clusters with the energy difference up to 0.22 eV per four atoms. The V–C2 pair is found to be as strong nucleation site for the solute-rich clusters as the V–C pair. Only Si solute atom stands out from the trend showing a weaker affinity to the V–C2 complex by 0.09 eV compared to the attraction to the V–C pair. The overall results point to the importance of taking into account the existence of both V–C and V–C2 complexes in studying the formation of solute-rich clusters in Fe-based steels for nuclear applications.
Keywords: Ferritic steels; Minor alloying elements; Carbon; Solute clusters; Ab initio calculations Registration No. 21513

The pH dependence of Am(III) complexation with acetate: an EXAFS study
Froehlich, D. R.; Skerencak-Frech, A.; Bauer, N.; Rossberg, A.; Panak, P. J.
Abstract: The complexation of acetate with Am(III) is studied as a function of the pH (1–6) by extended X-ray absorption fine-structure (EXAFS) spectroscopy. The molecular structure of the Am(III)–acetate complexes (coordination numbers, oxygen and carbon distances) is determined from the raw k3-weighted Am LIIIedge EXAFS spectra. The results show a continuous shift of Am(III) speciation with increasing pH value towards the complexed species. Furthermore, it is verified that acetate coordinates in a bidentate coordination mode to Am(III) (Am—C distance: 2.82 0.03 A ° ). The EXAFS data are analyzed by iterative transformation factor analysis to further verify the chemical speciation, which is calculated on the basis of thermodynamic constants, and the used structural model. The experimental results are in very good agreement with the thermodynamic modelling.
Keywords: americium; acetate; coordination chemistry; EXAFS; ITFA Registration No. 21512

Pushing the Limits of Ferromagnetic Resonance: Detection of Single sub-100-nm Nanodots
Lenz, K.; Banholzer, A.; Narkowicz, R.; Grebing, J.; Stienen, S.; Lindner, J.; Fassbender, J.
Abstract: Spintronic devices like MRAM, STNOs, or magnonic crystals are based on various types of magnetic nanostructures. Hence, it is crucial to know their magnetic properties, e.g., to allow for proper simulation for further development. The magnetic characterization in terms of magnetic damping, resonance modes, or magnetic anisotropy of single nanosized objects is very challenging, nevertheless of utmost importance, as otherwise bulk or film parameters need to be used for simulations.
Ferromagnetic resonance (FMR) is in principle the ultimate technique to measure such parameters. Unfortunately, conventional FMR based on resonant cavities and even modern broadband coplanar waveguide FMR lacks the sensitivity to measure single sub-micron-sized nano elements. Usually the detection limit of FMR, i.e. the minimum number of spins, which can be detected, is about 1012 spins for permalloy. Up to now, arrays of such elements had to be prepared to overcome this limit. However, great care on a homogeneous sample preparation has to be taken. For example, already slight inhomogeneities between the array's elements render the individual resonant modes of the nanostructures invisible, due to linewidth broadening.
For the analysis of single nanoobjects a much higher sensitivity is required. Using our recently developed microresonators [1,2] we show how single nanoelements down to sample diameters of 100 nm can be measured.
Taking the signal-to-noise ratio achieved so far into account, we extrapolate the detection limit to 105 spins. The uniform excitation mode as well as various localized modes like e.g. edge modes can be observed. Their state can be visualized with micromagnetic simulations.
References:
[1] A. Banholzer, et al., Nanotechnology 22, 295713 (2011).
[2] R. Narkowicz et al., Rev. Sci. Instrum. 79, 084702 (2008).

Keywords: ferromagnetic resonance, nanostructures, damping, spinwaves, microresonators
  • Lecture (Conference)
    59th Annual Magnetism and Magnetics Materials Conference, 04.-07.11.2014, Honolulu, Hawaii, USA
Registration No. 21510

Light emitting diode based on (In,Ga)As/GaAs coaxial multi-shell nanowires monolithically integrated on silicon
Dimakis, E.; Jahn, U.; Ramsteiner, M.; Tahraoui, A.; Grandal, J.; Trampert, A.; Biermanns-Föth, A.; Pietsch, U.; Riechert, H.; Geelhaar, L.
Abstract: We demonstrate the use of III-arsenide nanowires as light emitting diodes (LEDs) monolithically integrated on Silicon. LEDs made of (In,Ga)As/GaAs coaxial multi-shell nanowires were grown catalyst-free directly on Si(111) by molecular beam epitaxy (MBE). The active region consists of a single (In,Ga)As/GaAs quantum well in the radial direction (Fig. 1-a). Correlating the emission properties of the quantum wells (Fig. 1-b) with the growth kinetics on the ( ) side-walls, we were able to identify the optimal growth conditions for coherently strained quantum wells with high-quality interfaces and homogeneous structure (in terms of chemical composition and shell thicknesses) along the nanowire axes. Shell-doping methods were successfully employed for the realization of p- and n-type GaAs shells, while a planarization scheme with transparent ohmic contacts allowed massive biasing in parallel configuration of the free-standing nanowires on the Silicon substrate. Rectifying operation and room-temperature electroluminescence were obtained (Fig. 1-c), proving the great potential of this technology.
  • Invited lecture (Conferences)
    Nanowires 2013, 12.11.2013, Weizmann Institute of Science, Rehovot, Israel
Registration No. 21509

Magnetostatics and Dynamics of Ion Irradiated NiFe/Ta Multilayer Films Studied by Vector Network Analyzer Ferromagnetic Resonance
Markó, D.
Abstract: In the present work, the implications of ion irradiation on the magnetostatic and dynamic properties of soft magnetic Py/Ta (Py = Permalloy: Ni80Fe20) single and multilayer lms have been investigated with the main objective of nding a way to determine their saturation magnetization. Both polar magneto-optical Kerr eect (MOKE) and vector network analyzer ferromagnetic resonance (VNA-FMR) measurements have proven to be suitable methods to determine 0MS, circumventing the problem of the unknown eective magnetic volume that causes conventional techniques such as SQUID or VSM to fail. Provided there is no perpendicular anisotropy contribution in the samples, the saturation magnetization can be determined even in the case of strong interfacial mixing due to an inherently high number of Py/Ta interfaces and/or ion irradiation with high uences.
Another integral part of this work has been to construct a VNA-FMR spectrometer capable of performing both azimuthal and polar angle-dependent measurements using a magnet strong enough to saturate samples containing iron. Starting from scratch, this comprised numerous steps such as developing a suitable coplanar waveguide design, and writing the control, evaluation, and tting software.
With both increasing ion uence and number of Py/Ta interfaces, a decrease of saturation magnetization has been observed. In the case of the 10Py samples, an immediate decrease of 0MS already sets in at small ion uences. However, for the 1Py and 5Py samples, the saturation magnetization remains constant up to a certain ion uence, but then starts to rapidly decrease. Ne ion irradiation causes a mixing and broadening of the interfaces. Thus, the Py/Ta stacks undergo a transition from being polycrystalline to amorphous at a critical uence depending on the number of interfaces. The saturation magnetization is found to vanish at a Ta concentration of about 10{15 at.% in the Py layers. The samples possess a small uniaxial anisotropy, which remains virtually unaected by the ion uence, but slightly reduces with an increasing number of Py/Ta interfaces. In addition to magnetostatics, the dynamic properties of the samples have been investigated as well. The Gilbert damping parameter increases with both increasing number of Py/Ta interfaces and higher ion uences, with the former having a stronger in uence. The inhomogeneous linewidth broadening B0 increases as well with increasing number of Py/Ta interfaces, but slightly decreases for higher ion uences.

Keywords: ferromagnetic resonance, FMR, thin films, multilayers, ferromagnetism
  • Doctoral thesis
    TU Dresden, 2010
    Mentor: Jürgen Fassbender
    107 Seiten
Registration No. 21508

From 2D CoCrPt:SiO2 films with perpendicular magnetic anisotropy to 3D nanocones — A step towards bit patterned media
Ball, D. K.
Abstract: Due to the ever-increasing worldwide consumption of memory for digital information, new technologies for higher capacity and faster data storage systems have been the focus of research and development. A step towards achieving higher data storage densities for magnetic recording media is the concept of bit patterned media, where the magnetic recording layer is divided up into magnetically isolated bit units. This approach is one of the most promising technologies for increasing data storage densities and could be implemented by nanostructuring the wafer. Therefore, the fabrication of the appropriate nanostructures on a small scale and then be able to manufacture these structures on an industrial scale is one of the problems where science and industry are working on a solution. In addition, the answer to the open question about the influence that patterning on the nano length scale has on the magnetic properties is of great interest.
The main goal of this thesis is to answer the open question, which magnetic properties can be tailored by a modification of the surface texture on the nanometre length scale. For this purpose the following properties: anisotropy, remanence, coercivity, switching field distribution, saturation magnetisation, Gilbert damping, and inhomogeneous linebroadening were compared between planar two dimensional thin ferromagnetic films and three dimensional magnetic structures. In addition, the influences of the tailored morphology on the intergranular or the exchange coupling between the structures, which is called interdot exchange coupling, was investigated. For the ferromagnetic thin films, the focus of the investigations was on the granular CoCrPt:SiO2 and [Co/Pd] layer, which currently are the state-of-the-art material for magnetic data storage media. These materials are characterised by their high coercivity and high perpendicular anisotropy, which has a low spatial distribution in the preferred direction of magnetisation.
In this work the pre-structured GaSb(001) substrate with self-assembled periodic nanocone structures at the surface are used. The preparation by ion beam erosion of these structures is simple, fast, and highly reproducible and therefore this method is particularly beneficial for fundamental research. To compare the 2D thin films with the 3D magnetic structures, besides the pre-structured specimen, planar samples were also fabricated. The first sample series prepared was coated by Py. Due to the fact that the magnetic properties of this material are well-known, it was also possible to do some OOMMF simulations in addition to the VNA-FMR and MOKE measurements.
Afterwards two planar samples with CoCrPt and CoCrPt:SiO2 were prepared. The planar CoCrPt:SiO2 samples were Co+ ion implanted to study the influence of such irradiation on the intergranular and interdot exchange coupling, switching field distribution, and in particular on the spin dynamics. Moreover, both samples were measured by TRMOKE in order to obtain information about the spin dynamics.
Subsequently, the perpendicular storage media materials CoCrPt:SiO2 and [Co/Pd] were deposited on a prestructured GaSb(001) nanocone substrate surface. These sample series were measured by MOKE, SQUID, and vector-VSM. The measurements demonstrate the influence of the periodicity and height of the nanocones on the intergranular and interdot exchange coupling. They also show the reorientation of the magnetization with respect to the curvature of the substrate template and furthermore, the morphology-induced influences on the magnetic domains.
From the comparison between the results for the planar and the pre-structured samples, a decrease of the interdot exchange coupling was observed, which scales together with the periodicity of the nanocone pattern. In addition, it was shown that for all samples with thin magnetic films on nanocones,the magnetization aligns along the curvature of the underlying nanocone structure. For Py on nanocones, planar granular CoCrPt:SiO2, and planar granular CoCrPt, measurements by VNA-FMR and TRMOKE could be carried out, which yielded information about the spin dynamics. The results obtained for both of the planar sample are comparable to values from the literature for the Gilbert damping. The results for the Py samples showed that the commonly used 2D model resonance condition is, in case of a 3D magnetic structure, no longer valid due to the alignment of the magnetisation along the underlying substrate structure and therefore an new model has to be derived.

Keywords: Ferromagnetic resonance, VSM, ferromagnetism, MOKE, nanostructures, spin waves
  • Doctoral thesis
    TU Dresden, 2013
    Mentor: Jürgen Fassbender
    132 Seiten
Registration No. 21507

Method for evaluation of upgrading by liberation and separation
Leißner, T.; Mütze, T.; Atanasova, P.; Bachmann, K.; Peuker, U. A.
Abstract: A method is presented for the evaluation of mineral processing by liberation and upgrading. The method bases on the plot of recovery of valuables versus the recovery of gangue (Fuerstenau upgrading curve). The locking curve of a feed material was plotted together with the upgrading curve in a Fuerstenau diagram. The assessment of liberation and upgrading is done by a comparison of surfaces formed by the curves and some characteristic lines of the diagram. This plot allows the calculation of two new quantitative measures for liberation and upgrading.
Both parameters can be combined to a third parameter describing the quality of the whole technical setup for mineral processing by subtracting the upgrading parameter from the liberation parameter. The third parameter shows a positive value in cases of upgrading determined processes, a negative value in cases of liberation affected processes and about zero for processes affected equally by liberation and upgrading. Thus it is easily possible to distinguish between poor results in the mineral processing caused by insufficient liberation or poor results caused by insufficient upgrading. Preliminary results from two case studies, performed on two different ore types, are very promising illustrating the practical use of such an approach.

Keywords: flotation modeling, optimization, process development
  • Contribution to proceedings
    XXVII International Congress on Mineral Processing, 20.-24.10.2014, Santiago de Chile, Chile
    Proceedings of the XXVII International Mineral Processing Congress – IMPC 2014, 1-10
Registration No. 21506

Morphology-Induced Magnetic Phenomena Studied by Broadband Ferromagnetic Resonance
Körner, M.
Abstract: In the present work, the influence of the morphology of thin ferromagnetic films on their static as well as dynamic magnetic properties was investigated by means of broadband ferromagnetic resonance (FMR). Using an ion beam erosion process the surface of the substrates was periodically modulated (ripples), where the modulation wavelength is determined by the ion energy. In this way a well-controllable roughness profile evolves ranging from a few ten up to several hundreds of nanometers in wavelength. The substrate’s surface profile in turn is repeated by films grown on top offering an easy and fast approach to investigate morphology influences on the magnetic properties. This work aims on modifications of the magnetic anisotropy as well as the FMR linewidth of the magnetic relaxation process.
Prior to magnetic investigations the existing FMR setup was extended to measure FMR spectra at a fixed microwave frequency while sweeping the external magnetic field. Furthermore, a software toolbox was developed to perform the data processing and evaluation.
Starting with the morphology influence on the magnetic anisotropy 10 nm thin Fe, Co, and Ni81Fe19 (Permalloy Py) films were deposited on rippled Si substrates. Due to Si displacements during ion erosion and natural oxidation the rippled Si substrates exhibit an amorphous surface causing a polycrystalline material growth. This leads to a suppression of magneto-crystalline anisotropy leaving only morphology-induced anisotropy contributions.
Here, a uniaxial magnetic anisotropy (UMA) was observed that aligns its easy axis with the ripple ridges, whereas its strength decays with increasing ripple wavelength for all materials. From thickness-dependent measurements two characteristic regions were determined with competing uniaxial volume and surface anisotropy contributions. Underlined by micromagnetic simulations a dominant volume contribution was found in the thin region accompanied by magnetic moments nearly following the surface corrugation. In the thick region the UMA is controlled by dipolar stray fields at the surface.
In contrast to Si, ion eroded MgO keeps its crystal structure offering epitaxial growth of 10 nm thin single-crystalline Fe films. Consequently, a superposition of morphology-induced UMA and magneto-crystalline cubic anisotropy was observed. The direction of the ripple ridges is predetermined by the incident ion beam, which allows to freely orient the UMA’s direction with respect to the cubic anisotropy, offering a possibility for anisotropy engineering. In comparison to the planar reference case rippled magnetic films exhibit lower intrinsic and extrinsic relaxation contributions.
For the final part, 30 nm Py was grown on rippled Si covering modulation wavelengths l ranging from 27 to 432 nm. Using magnetic force microscopy and holography measurements the dipolar stray fields above and inside the magnetic layer were characterized. For l 222 nm, the stray fields act as scattering centers for spin waves triggering two-magnon scattering (TMS). This causes an apparent line broadening generating distinct peaks in the frequency-dependent linewidth whose position can be tuned by altering l. These effects are understood in the framework of a perturbation theory of spin waves in periodically perturbed films recently presented in the literature. Furthermore, the in-plane angular dependence of the linewidth revealed a two-fold symmetry, which is not present for vanishing TMS at small l.

Keywords: ferromagnetic resonance, ferromagnetism, FMR, thin films, spin waves
  • Doctoral thesis
    TU Dresden, 2013
    Mentor: Jürgen Fassbender
    185 Seiten
Registration No. 21505

Polytypism in GaAs nanowires: determination of the interplanar spacing of wurtzite GaAs by X-ray diffraction
Köhl, M.; Schroth, P.; Minkevich, A. A.; Hornung, J.-W.; Dimakis, E.; Somaschini, C.; Geelhaar, L.; Aschenbrenner, T.; Lazarev, S.; Grigoriev, D.; Pietsch, U.; Baumbach, T.
Abstract: In GaAs nanowires grown along the cubic [111]c direction, zinc blende and wurtzite arrangements have been observed in their stacking sequence, since the energetic barriers for nucleation are typically of similar order of magnitude. It is
known that the interplanar spacing of the (111)c Ga (or As) planes in the zinc blende polytype varies slightly from the wurtzite polytype. However, different values have been reported in the literature. Here, the ratio of the interplanar spacing of these polytypes is extracted based on X-ray diffraction measurements for thin GaAs nanowires with a mean diameter of 18–25 nm. The measurements are performed with a nano-focused beam which facilitates the separation of the scattering of nanowires and of parasitic growth. The interplanar spacing of the (111)c Ga (or As) planes in the wurtzite arrangement in GaAs nanowires is observed to be 0.66% 0.02% larger than in the zinc blende arrangement.

Keywords: GaAs; nanowires; polytypism; X-ray diffraction; nanofocus Registration No. 21504

Analyse eines Messplatzes für frequenzaufgelöste magnetooptische Kerr-Effektmessungen (FR-MOKE) sowie dessen Ansteuerung auf der Basis von LabVIEW
Trache, M.
Abstract: keines Vorhanden
Keywords: ferromagnetism, ferromagnetic resonance, MOKE, FR-MOKE
  • Diploma thesis
    Wilhelm Büchner Hochschule, 2012
    Mentor: Kilian Lenz
    80 Seiten
Registration No. 21503

Untersuchung der elektrischen und magnetischen Eigenschaften von BiFeO3-Filmen
Noack, H.
Abstract: keines vorhanden.
Keywords: ferromagnetism, ferromagnetic resonance, ferroelectrics
  • Diploma thesis
    Wilhelm Büchner Hochschule, 2011
    Mentor: Kilian Lenz
    94 Seiten
Registration No. 21502

Magnetische Charakterisierung dünner Keilschichten mittels frequenzaufgelöstem magnetooptischen Kerr-Effekt
Hoffmann, S.
Abstract: Im Rahmen dieser Arbeit wurden erstmalig ein Probensystem aus zwei ferromagnetischen Fe3Si Schichten und einer keilförmigen Magnesiumoxid (MgO) Zwischenschicht, mittels der Kombination von ferromagnetischer Resonanz (FMR) und magnetooptischer Detektion mit Hilfe des Kerr-Effekts (MOKE), am FR-MOKE Aufbau untersucht. An verschiedenen Stellen der Probe wurden frequenzabhängige Messungen durchgeführt, um daraus Rückschlüsse auf die magnetischen Eigenschaften des Materials zu ziehen. Durch den Vergleich mit Literaturwerten konnte gezeigt werden, dass mithilfe dieser Messmethode durchaus zuverlässige Messungen durchgeführt werden können. Anhand der aufgenommen Spektren wurde der Gradient in der Probe nachgewiesen, sowie die Abhängigkeit der Interlagenaustauschkopplung von der Zwischenschichtdicke verdeutlicht.
Keywords: magnetism, ferromagnetic resonance, MOKE, thin films
  • Bachelor thesis
    TU Ilmenau, 2014
    Mentor: Kilian Lenz
    50 Seiten
Registration No. 21501

Impact of strain induced by polymer curing in benzocyclobutene embedded semiconductor nanostructures
Bussone, G.; Dimakis, E.; Grifone, R.; Biermanns, A.; Tahraoui, A.; Carbone, D.; Geelhaar, L.; Schülli, T. U.; Pietsch, U.
Abstract: Polymers such as benzocyclobutene are commonly used as embedding materials for semiconductor nanostructures. During the curing process of the polymer up to 250 °C, a significant impact of strain can be induced on the embedded semiconductor material due to different thermal expansion coefficients. This strain has been revealed by X-ray diffraction in free-standing GaAs nanowires grown on a silicon substrate, embedded in a polymer matrix. It will be shown that this strain is released during the X-ray irradiation if additionally an external static electric field is applied.
Keywords: benzocyclobutene; polymer matrix; X-ray diffraction; embedded semiconductor nanostructures; GaAs nanowires; strain Registration No. 21499

Untersuchung der magnetischen Eigenschaften von Permalloy-Filmen mittels frequenzaufgelöstem magnetooptischen Kerr-Effekt (FR-MOKE)
Rupp, S.
Abstract: Im Rahmen dieser Arbeit wurden dünne ferromagnetische Filme aus Permalloy (Ni80Fe20) mit eine Kombination aus ferromagnetischer Resonanz (FMR) und magnetooptischem Kerr-Effekt (MOKE) auf ihre dynamischen Eigenschaften hin untersucht. Das Hauptmerkmal dieser frequenzaufgelösten FR-MOKE Messung lag hierbei auf der Bestimmung der Linienbreite zur Charakterisierung der wirksamen Dämpfung der Magnetiserungspräzession und des g-Faktors für Permalloy. Die Ergebnisse im Einzelnen sind: 1. Die Linienbreite kann im Bereich von 1-25 GHz bestimmt werden. 2. Die Linienbreite steigt mit der Mikrowellenfrequenz f linear an und besitz einen geringen inhomogenen Anteil. 3. Die Amplitude der Lorentzkurve fällt mit 1/f ab. 4. Bestimmung des g-Faktors g=2,085(11), für Permalloy. 5.
Die Dämpfung ist konstant und beträgt alpha=0,007.

Keywords: ferromagnetism, ferromagnetic resonance, thin films, MOKE
  • Bachelor thesis
    nta Naturwissenschaftlich-Technische Akademie Prof. Dr. Grübler gGmbH, 2014
    Mentor: Kilian Lenz
    54 Seiten
Registration No. 21498

Role of liquid indium in the structural purity of wurtzite InAs nanowires that grow on Si(111)
Biermanns, A.; Dimakis, E.; Davydok, A.; Sasaki, T.; Geelhaar, L.; Takahasi, M.; Pietsch, U.
Abstract: InAs nanowires that grow catalyst-free along the [111] crystallographic orientation are prone to wurtzite-zincblende polytypism, making the control of the crystal phase highly challenging. In this work, we explore the dynamic relation between the growth conditions and the structural composition of the nanowires using time-resolved X-ray scattering and diffraction measurements during the growth by molecular beam epitaxy. A spontaneous buildup of liquid indium is directly observed in the beginning of the growth process and associated with the simultaneous nucleation of InAs nanowires predominantly in the wurtzite phase. The highly arsenic-rich growth conditions that we used limited the existence of the liquid indium to a short time interval, which is defined as the nucleation phase. After their nucleation, the nanowires grow in the absence of liquid indium, and with a highly defective wurtzite structure. Complementary ex-situ diffuse X-ray scattering measurements and modeling revealed that this structural degradation is due to the formation of densely spaced stacking faults. Thus, high wurtzite phase purity is associated with the presence of liquid indium. This finding implies that pure wurtzite nanowires may be obtained only if the growth is performed under the continuous presence of liquid indium at the growth interface, that is, in the vapor–liquid–solid mode.
Keywords: nanowires; InAs; Si; molecular beam epitaxy (MBE); X-ray diffraction Registration No. 21497

Two-dimensional electron gas in monolayer InN quantum wells
Pan, W.; Dimakis, E.; Wang, G. T.; Moustakas, T. D.; Tsui, D. C.
Abstract: We report in this letter experimental results that confirm the two-dimensional nature of the electron systems in a superlattice structure of 40 InN quantum wells consisting of one monolayer of InN embedded between 10 nm GaN barriers. The electron density and mobility of the two-dimensional electron system (2DES) in these InN quantum wells are 51015cm2 (or 1.251014cm2 per InN quantum well, assuming all the quantum wells are connected by diffused indium contacts) and 420 cm2/Vs, respectively. Moreover, the diagonal resistance of the 2DES shows virtually no temperature dependence in a wide temperature range, indicating the topological nature of the 2DES. Registration No. 21496

Status of the ELBE SRF Gun II
Arnold, A.
Abstract: As in 2007 the first 3.5 cell superconducting radio frequency (SRF) gun was taken into operation, it turned out that the specified performance has not been achieved. However, to demonstrate the full potential of this new type of electron source, a second and slightly modified SRF gun II was built in collaboration with Thomas Jefferson National Accelerator Facility (TJNAF). We will report on commissioning and first results of the new gun, which includes in particular the characterization of the most important RF properties as well as their comparison with previous vertical test results.
Keywords: superconducting electron injector, SRF gun, ELBE
  • Lecture (others)
    HOPE / SINEMP project meeting, 03.-04.11.2014, Siegen, Deutschland
Registration No. 21494

System Integration and Application of CdZnTe Detectors in a Compton Camera for Medical Use
Fiedler, F.; Enghardt, W.; Golnik, C.; Hueso-Gonzales, F.; Kormoll, T.; Schumann, A.; Pausch, G.; Petzold, J.; Rohling, H.; Roemer, K.; Schoene, S.
Abstract: Ion beams offer advantages over conventional treatment modalities, such as photons. Because of the way ions deposit their energy on their path through tissue they allow for an increased dose deposition in the tumor volume and reduce the collateral damage to the surrounding healthy tissue. However, the range of these particles is sensitive to small density changes in the irradiated volume. Deviations will lead to a misalignment of the deposited dose maximum and the tumor. It is therefore highly desirable to verify the particle range in-vivo and in realtime by means of a detector system independent from the treatment device. One approach is to monitor the prompt gamma-ray emissions from excited nuclei that originate in the interaction of projectile and target nuclei. A Compton camera could be one of the feasible technical solutions for such a monitoring system. To set up a clinical applicable device a comprehensive modelling of the creation of secondary radiation as well as of the detection process is required. Furthermore, a sophisticated reconstruction of the data is essential. This paper will present three different prototypes of such a detector system made of CdZnTe and scintillation detectors. Also we will show measurements on the detector performance as well as reconstructed images of the radiation sources.
Keywords: Compton camera, in-vivo dose imaging, proton therapy, CdZnTe detectors
  • Invited lecture (Conferences)
    IEEE NSS MIC, 21st Symposium on room-temperature Semiconductor and Gamma-Ray detectors, 08.-15.11.2014, Seattle, WA, USA
Registration No. 21493
Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194]