Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Übersicht zur r³ Fördermaßnahme (Präsentation auf PIUS Länderkonferenz)

A benchmark analysis was launched within the Work Package on Core Safety of the EU FP7 cross-cutting project supporting the European Sustainable Industrial Initiative (ESNII), named ESNII+, aimed at providing a quantitative estimation of the uncertainties affecting the calculation of both core static neutronic parameters and safety coefficients of a Sodium-cooled Fast Reactor (SFR) low-void-effect core similar to the one considered for the Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID). Established deterministic and stochastic neutronic codes, as well as different nuclear data libraries, were employed by eight European organizations to perform a complete core characterization, with the ultimate goal to achieve consensus on computational methods and associated databases to be employed for advanced-design SFRs safety analyses. The comparison of the results obtained by the participating institutions provided quantitative information about capabilities and limitations of the different approaches, and about library effects, by highlighting the sensitivity of safety parameters to both computational techniques and nuclear data. Selected results of the first phase of the benchmark are presented and analyzed, along with a discussion of the planned R&D activities needed to improve the present benchmark status.

Atomic force microscopy (AFM) and the colloidal probe mode allow for the first time the direct measurement of particle interactions. Thus, it is the direct way to evaluate the adhesion of particles to surfaces or to each other. With the direct measurement it is significantly easier to quantify the effect of changing surface properties on the interaction forces. Several surface properties influence the interaction forces like surface roughness, local chemical composition (e.g. adsorbed surfactants), electrostatic charge and surface energies.
Phase contrast AFM
The non-contact mode of AFM also allows characterizing the composition of a heterogeneous surface like that of a nano-composite material, with a high resolution, which is comparable to TEM. For this method, it is not necessary to prepare translucent samples, but only to minimize the surface roughness, e.g. by polishing to avoid a secondary signal.
Colloidal Probe AFM (dry)
The colloidal probe provides the real adhesion effects taking into account both the roughness of the substrate as well as that of the particle.
Colloidal Probe AFM (wet - liquid cell)
The colloidal probe measurements in the liquid phase allow quantifying the surface modification due to adsorption from the aqueous phase to the substrate, or to the particle at the cantilever itself. This adsorption of surfactants like modifiers or flotation collectors becomes visible as well as an interaction of the surface with one component of a water-alcohol mixture. The detection of nano-bubbles, which are one source of strong hydrophobic interactions, is also possible.

Der Heterokoagulationsprozess Flotation ist eines der bedeutendsten Verfahren in der Aufbereitungstechnik und ein Schwerpunkt der Forschung am Helmholtz-Institut Freiberg für Ressourcentechnologie. Die Trennung basiert auf den unterschiedlichen Benetzbarkeiten von suspendierten (Mineral)partikeln, die zumeist durch selektiv adsorbierende amphiphile Moleküle beeinflusst werden. Häufig wurden in der Flotationsforschung für die Benetzungsbeschreibung die Kontaktwinkel zu Wasser herangezogen und mit dem Flotationsausbringen korreliert. Eine fundamentalere Charakterisierung der Mineraloberfläche basiert auf der Bestimmung der spezifischen freien Oberflächenenergien, die zusammen mit den spezifischen freien Oberflächenenergien von Wasser die Benetzung über die Young-Gleichung beschreiben. Die Inverse Gas Chromatographie (iGC) ist eine geeignete Methode die spezifischen freien Oberflächenenergieanteile und deren Verteilung an Partikelsystemen zu bestimmen. Jedoch erfolgt diese Messung an trockenen Pulverschüttungen und nicht an suspendierten Partikeln. Um den Einfluss von oberflächenaktiven Flotationsreagenzien auf die Flotierbarkeit und damit korrelierend auf die Oberflächenenergien zu bestimmen ist es daher notwendig die Art und Weise der Probenpräparation für die iGC nach Konditionierung mit Flotationsreagenzien in Wasser zu untersuchen.
In dieser Arbeit werden die Minerale Quartz (SiO2), Apatit (Ca5[F,(PO4)3]) und Magnetit (Fe3O4) auf ihre Flotierbarkeit und Oberflächenenergie für unterschiedliche Probenpräparationen untersucht sowie der Einfluss der ionischen Sammler Natriumoleat (kationisch) und Dodecyl Ammonium Acetat (anionisch), welche chemi- bzw. physisorbieren aufgezeigt. Es wird diskutiert, welcher Parameter der spezifischen freien OberIflächenenergien (und deren Verteilung) am ehesten die Hydrophobizität beschreibt und somit einen wichtigen Einfluss auf die Flotierbarkeit eines Mineralpartikels beinhaltet, also mit dem Flotationsausbringen der Mikroflotation korreliert.

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.

Spätestens seit dem Patent der Gebrüder Bessel aus Dresden von 1877 nutzt man die Anhaftung hydrophober Partikel an Gasblasen in der Flotation, einer Heterokoagulationstrennung, technologisch aus, um Partikelgemische auf Basis ihrer chemisch veränderlichen Benetzungseigenschaften voneinander zu trennen. Ein wesentlicher Mikroprozess ist hierbei der Anlagerungsvorgang, bestimmt durch das Wechselwirkungspotential zwischen einem Partikel und einer Gasblase. Die klassische DLVO Wechselwirkungstheorie beinhaltet für diese Partner nur repulsive Terme, d.h. abstoßende Doppelschichtwechselwirkungen und abstoßende van der Waals Wechselwirkungen durch eine negative Hamaker-Konstante. Über die Physik der zwingend notwendigen, weil prozessbestimmenden, weit reichenden, anziehenden Wechselwirkungskomponente ist man sich in der Literatur noch nicht einig. Viele Wissenschaftler sehen feinste Gasdomänen auf hydrophoben Oberflächen, oft als Nanobubbles oder Micropancakes bezeichnet, als Vermittler von weit reichenden kapillaren Anziehungskräften. Andere sehen eine weit reichende Wasserstrukturstörung an hydrophoben Oberflächen als Ursache für eine somit entropisch begründete Anziehung.
Am Helmholtz-Institut Freiberg für Ressourcentechnologie werden atomare Gesamtwechselwirkungen zwischen unterschiedlich benetzenden Oberflächen (z. B. Mineralen) und hydrophoben Modellpartikeln in Lösung mit Hilfe der Partikelsonden Rasterkraftmikroskopie analysiert. Mit diesen Untersuchungen soll es später möglich werden, die Flotierbarkeit von Mineralen in Erzschliffen als Funktion der physikalisch chemischen Variablen direkt zu untersuchen. Zudem wird ein Beitrag geleistet um die noch stark diskutierten Mechanismen der Anhaftung hydrophober Partikel an Gasblasen letztlich zu klären. Am Poster wird der aktuelle Forschungsstand kurz reflektiert, die Methode der Partikelsonden Rasterkraftmikroskopie vorgestellt und experimentell verifiziert an den Mineralen Magnetit und Quarz unter Einwirkung unterschiedlicher ionaktiver Sammler im Vergleich zu Mikroflotationsuntersuchungen an der Hallimond-Röhre.

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.

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.

The German government has decided for the nuclear phase out, but a decision on a strategy for the management of the highly radioactive waste is not defined yet. Partitioning and Transmutation (P&T) could be considered as a technological option for the management of highly radioactive waste, therefore a wide study has been conducted. In this group objectives for P&T and the boundary conditions of the phase out have been discussed. The fulfillment of the given objectives is analyzed using simulations of molten salt reactors with fast neutron spectrum. It is shown that the efficient transmutation of all existing transuranium isotopes would be possible in a time frame of about 60 years using three reactors and a twofold life cycle consisting of a transmuter operation and a deep burn phase. A basic insight for the optimization of the time duration of the deep burn phase is given. Further on a detailed balance of different isotopic inventories is given to allow a deeper understanding of the processes during transmutation and the effect of modelling and simulation is investigated based on three different modelling strategies and two different code versions.

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.

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.

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].

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

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.

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.

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.

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.

Flotation 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 (iGC) 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 floatability 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 paper different minerals (quartz, apatite and magnetite) and ionic collectors (anionic sodium oleate and cationic dodecyl ammonium acetate) with crucially different surfactant adsorption mechanisms are used to determine floatability (microflotation) and specific surface free energy distributions (iGC) 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 are put in context and discussed. A proper presentation of the surface free energy components is presented giving a quantitative description of hydrophobicity. There will also be a short introduction to and discussion of the method of inverse Gas Chromatography as it is rather new in the field of mineral processing.

This paper reviews rare earth minerals (monazite and xenotime) separation by flotation. A wide range of monazite and xenotime flotation test results are reviewed including: reasons of variation in the point of zero charges on these minerals, the effects of various flotation conditions on zeta potential and the point of zero charges on the surface of monazite and xenotime, interactions of collectors and depressants on the surface of these mineral phases during flotation separation, relationship between surface chemistry of the minerals and different types of collector adsorptions, effects of the conditioning temperature on flotation of rare earth minerals. This review summarizes various approaches for selective separation of monazite and xenotime by flotation for further research in future.

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

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.

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.

Secondary raw materials are becoming increasingly more important in ensuring the stability of critical metal supply. Ashes, slags, dusts and other industrial residues are produced in large quantities.
Precise and accurate chemical and mineralogical data, knowledge of distribution of valuable and deleterious elements in the single phases as well as information about homogeneity and grain size distribution of the minerals are crucial for the development of new extraction technologies.
Gaining these essential information can be achieved by using SEM-based automated mineralogical analysis. However, the large particle size range, the dominance of very small grain sizes (< 5 µm) and the diversity of phases are challenging for the analysis. Furthermore, in contrast to natural materials the analysis of secondary materials faces the challenge of developing new methods for non-natural extreme combinations of elements and phases. Initial results of ash and slag samples will be presented and evaluated.

The distribution of the electromagnetic dipole strength below the neutron separation energy and its influence on the photon distribution after neutron capture was investigated in a twin experiment for the compound nucleus 114Cd. The experimentally deduced spectra after photon scattering on 114Cd and the neutron capture in 113Cd were analyzed in matters of electro magnetic strength function and nuclear level density. By measuring the photoabsorption cross section at the bremsstrahlung facility gammaELBE at the Helmholtz-Zentrum Dresden-Rossendorf it was possible to deduce information about the distribution of dipole strength below the neutron separation energy. The deexcitation spectrum after cold-neutron capture in 113 Cd was calculated and different magnetic dipole strength function models were tested with the help of the statistical code gammaDEX.

The Dy₂Fe₁₇H_x 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 T_C = 375 K and a spontaneous moment of 16.5 μ_B/f.u. Magnetization curves recorded for two different crystal orientations for Dy₂Fe₁₇H_x 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 μ_B is derived for Dy₂Fe₁₇H_3.8 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 n_Dy-T coefficient from about 3.3 down to 2.82 T f.u./μ_B for Dy₂Fe₁₇ and Dy₂Fe₁₇H_3.8, respectively.

PIConGPU is currently the fastest particle-in-cell code available. This talk explains how using GPUs increased the performance of this simulation code making parameter scans of previously hard to compute plasma setups possible. Additionally newly developed techniques are discussed and an outlook on simulations of foil targets and high harmonic generation are presented.

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.

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.

Positron-Emission-Tomography (PET) has favourable characteristics for monitoring the propagation of tracers in opaque media on the drill core scale. PET directly yields quantitative tracer concentrations, without retroaction on the process, with ultimate sensitivity (less than 109 atoms per voxel) and selectivity, with negligible matrix effect, and with expedient spatial resolution. It only requires radiolabelling of the observed substance with a positron-emitting isotope and therefore allows investigating processes in fluids without physical or compositional contrasts.
PET is a widely applied nuclear medical technique for 3D functional imaging. Since 1988 [1], some exemplary applications for the visualization of flow processes in various rock formations and other non-medical applications were conducted with clinical PET scanners with low spatial resolution and with short living radionuclides (e.g. ¹⁸F, T_1/2=109.77 min).
In contrast, we take advantage of a high-resolution PET-scanner, originally dedicated for biomedical research on small animals, with a resolution at the physical limit of 1 mm [2]. Also, we are able to conduct long-time experiments in our laboratory, applying radionuclides with longer lifetimes (e.g. ²²Na, T_1/2=2.602 a).
Our applications cover conservative and reactive flow of solutes and particles in soils and rocks, as well as diffusion processes in clays [3]. We strive to characterize heterogeneous transport effects on the basis of our visualisations of the propagation of the tracer. Frequently, we observe the evolution of strongly localized pathways, which depict the reduced effective volume, coming along with a reduced efficiency of the internal surface area for sorption processes. Our data can be used also for experimental calibration and verification of computer simulations of transport processes.
REFERENCES
[1] van den Bergen, E.A., Jonkers, G., Strijckmans, K., Goethals, P., 1989. Industrial Applications of Positron Emission Computed Tomography. Nuclear Geophysics 3, pp. 407-418.
[2] Zakhnini, A., Kulenkampff, J., Sauerzapf, S., Pietrzyk, U. and Lippmann-Pipke, J., 2013. Monte Carlo simulations of GeoPET experiments: 3D images of tracer distributions (¹⁸F, ¹²⁴I and ⁵⁸Co) in Opalinus Clay, anhydrite and quartz. Computers & Geosciences, 57: 183-196.
[3] Kulenkampff, J.; Gründig, M.; Korn, N.; Zakhnini, A.; Barth, T.; Lippmann-Pipke, J., 2013. Application of high-resolution positron-emission-tomography for quantitative spatiotemporal process monitoring in dense material. 7. World Congress on Industrial Process Tomography, Krakow, Poland, free available on http://www.isipt.org/world-congress/7/902.html

The Color X-ray Camera, type SLcam®, can detect X-ray radiation with spatial and energy resolution. The device is used as an X-ray detector in applications at synchrotrons and on PIXE beamlines. The unique properties of SLcam®, a combination of a single photon counting CCD with a polycapillary optics objective, allows a fast overview over a large detection area with first results visible almost immediately.
The maximal field of view exceeds 1 cm² and the spatial resolution can Approach several microns when using a sub-pixel algorithm.

Defect-induced ferromagnetism has triggered a lot of investigations and controversies. The major issue is that the induced ferromagnetic signal is so weak that it can be sufficiently accounted for by trace contamination. To resolve this issue, we studied the variation of the magnetic properties of SiC after neutron irradiation with fluence covering four orders of magnitude. A large paramagnetic component has been induced and scales up with defect concentration, which can be well accounted for by uncoupled divacancies. However, the ferromagnetic contribution is still weak and only appears in the low fluence range of neutrons or after annealing treatments. First-principles calculations hint towards a mutually exclusive role of the concentration of defects: A higher defect concentration favors a larger magnetic interaction at the expense of spin polarization. Combining both experimental and first-principles calculation results, the defect-induced ferromagnetism can probably be understood as a local effect which cannot be scaled up with the volume.

Results on the production of the double strange cascade hyperon Xi(-) 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 Xi(-) production is observed in proton-nucleus interactions. Assuming a Xi(-) phase-space distribution similar to that of. hyperons, the production probability amounts to P Xi- = [2.0 +/-0.4(stat) +/- 0.3(norm) +/- 0.6(syst)] x 10(-4) resulting in a Xi(-)/d(Lambda + Sigma(0)) ratio of P Xi-/P Lambda+Sigma 0 = [1.2 +/-0.3(stat) +/- 0.4(syst)] x 10(-2). Available model predictions are significantly lower than the measured Xi(-) yield.

For the long-term storage of radioactive waste in salt rock formations it is important to know how microorganisms can affect the performance of a repository. It is possible that in salt rock indigenous microbes are able to influence the oxidation state, the speciation and hence the solubility of actinides. So the migration of actinides can be reduced or enhanced by different processes as for example by biosorption with cellular ligands [1].
The biosorption capacity of the archaea Halobacterium noricense DSM 15987, which was used as a reference strain due to its worldwide occurrence in salt rock, was investigated. The strain was isolated from an Austrian salt mine [2] and similar species were also found in the WIPP (Waste Isolation Pilot Plant, Carlsbad, New Mexico, USA) [3]. This rod shaped microorganism is a halophilic one which requires at least 2.1 M NaCl whereat the optimum is 3.0 M NaCl [2].
Independent of the uranium concentration (10 – 120 µM) Halobacterium noricense DSM 15987 shows good sorption capabilities at room temperature (RT). Constantly, 90 % of added uranium was bound on the cells. Looking at the time dependence of biosorption with a constant uranium concentration (100 µM) an asymptotic sorption curve was obtained. This accumulation kinetic indicates a two stage process.
Directly after the addition of uranium it is rapidly sorbed by the cells. After 3 h 35 % of uranium was accumulated. The second slower step is reached after 42 h, where 90 % of added uranium was bound to the cells. Under these conditions this corresponds to 37.5 ± 0.7 mg U(VI) per 1 g dry biomass. A slightly faster sorption can be seen at higher temperatures especially at 50 °C. There the maximal sorption of 90 % is already reached after 24 h.
Interestingly, with increasing incubation time, uranium concentration and also temperature an agglomeration of the cells occurred. Live/Dead staining showed that agglomerated cells were mostly alive but nearly all single cells were dead. So we conclude that this agglomeration process is a kind of stress response to protect the cells themselves for environmental challenges.
Furthermore, the supernatant and the washed cell suspension were analysed with TRLFS to characterize the binding of uranium to the cells. Despite the high quenching effect of chloride to uranium fluorescence a luminescence signal could be detected. The reason is the high quantum yield of some formed complexes. With parallel factor analysis (Parafac) we could assume that two uranium-cell-complexes were formed. Species 1 is difficult to interpret due to the unspecific form of the spectrum. Further investigations with reference substances have to be done. But comparing with literature we assign species 2 to a carboxylic cell-uranyl-complex [4]. These results were confirmed by IR spectroscopy where as well carboxylic vibrations could be detected.
The archaeum Halobacterium noricense DSM 15987 shows good uranium sorption efficiencies. Independent of the occurring agglomeration always 90 % of the added uranium was bound to the cells. The binding of uranium to carboxylic groups on the cell wall was proven with TRLFS and IR spectroscopy. A binding of uranium to phosphate groups is still under investigation.
Thanks to Sabrina Gurlit for analysing the samples with ICP-MS and Karsten Heim for recording the IR-spectra.

REFERENCES
1. Morris, K. et al., “Biogeochemical cycles and remobilisation of the actinide elements” Interactions of microorganisms with radionuclides, Volume 2, Page 101-141 (2002).
2. Gruber, C. et al., “Halobacterium noricense sp. nov., an archaeal isolate from a bore core of an alpine Permian salt deposit, classification of Halobacterium sp. NRC-1 as a strain of H. salinarum and emended description of H. salinarum” Extremophiles, 8, Page 431-439 (2004).
3. Swanson, J. S. et al., “Status Report on the Microbial Characterization of Halite and Groundwater Samples from the WIPP” Status report Los Alamos National Laboratory, Page 1ff. (2012).
4. Vogel, M. et al., “Biosorption of U(VI) by the green algae Chlorella vulgaris in dependence of pH value and cell activity” Science of the Total Environment , Page 384-395. (2010).

Ferromagnetism can occur in wide-band gap semiconductors as well as in carbon-based materials, when specific defects are introduced. It is thus desirable to establish a direct relation between the defects and the resulting ferromagnetism. Here, we contribute to revealing the origin of defect-induced ferromagnetism using SiC as a prototypical example. We show that the long-range ferromagnetic coupling can be attributed to the p electrons of the nearest-neighbor carbon atoms around VSiVC divacancies. Thus, the ferromagnetism is traced down to its microscopic, electronic origin.

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).

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.

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.

The long-term disposal of radioactive wastes in a deep geological repository is the accepted international solution for the treatment and management of these special residues. The microbial community of the selected host rocks and engineered barriers for the deep geological repository may affect the performance and the safety of the radioactive waste repository. In this work the bacterial community of bentonite formations of Almeria (Spain), selected as reference material for bentonite engineered barriers in the disposal of radioactive wastes, was studied. 16S rRNA gene-based approaches were used to study the bacterial community of the bentonite samples by traditional clone libraries and Illumina-sequencing. A high bacterial diversity was found by both techniques, with phylotypes belonging to 13 different bacterial phyla: Acidobacteria, Actinobacteria, Armatimonadetes, Bacteroidetes, Choloroflexi, Cyanobacteria, Deinococcus-Thermus, Firmicutes, Gemmatimonadetes, Planctomycetes, Proteobacteria, Nitrospirae and Verrucomicrobia. The dominant groups of the community were mainly represented by Proteobacteria and Bacteroidetes.
Some of the identified genera were previously described for their capacity to interact with iron and different heavy metals as well as radionuclides, as for example, Acidovorax, Ralstonia, Variovorax and Sphingomonas. The results obtained in this work demonstrate the high bacterial diversity of these Spanish bentonite formations, and their possible negative effect on the structure of the clay minerals as well as interactions with different radionuclides, which may affect the safety of the deep geological repository of radioactive wastes.

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.

Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis — Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid–base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements.
Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core–shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions.
The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications.

Most of the steel in the world is produced by continuous casting, where liquid metal flows from a tundish through a submerged entry nozzle into a copper mould. The mould is cooled by water, so a solid shell starts to form at the mould walls. The resulting steel strand is pulled out of the mould continuously and solidifies completely.
In industry it is well-known that an unstable flow in the mould has negative effects on the resulting steel’s quality. Electromagnetic brakes (EMBr) are expected to dampen instabilities, although their impact on the flow can hardly be examined directly in liquid steel. In spite of the casting method’s economical and industrial importance, only a few simple measurement techniques are available to investigate the actual flow patterns in the mould. A more sophisticated technique for liquid metal flow measurements could help to resolve the open issues in the mould flow.
The contactless inductive flow tomography (CIFT) is a technique that measures the mean global flow of an electrically conducting melt by exposing it to a magnetic excitation field and measuring the flow induced perturbations of that field outside the melt. The velocity profile can then be calculated by solving an inverse problem, using adequate regularization techniques to deal with the non-uniqueness.
We present preliminary results for a physical model of a mould with a rectangular cross-section of 140 × 35 mm 2 in the presence of an EMBr. Additionally we show flow reconstructions for a 400 × 100 mm 2 mould, demonstrating the upward scalability of CIFT.

Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ≈ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability.

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.

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.

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

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

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.

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.

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).

For about a decade we apply positron emission tomography (PET) as molecular imaging modality for non-destructive process visualisation in geological material on laboratory scale [1]. Sequential PETimages directly yield the spatiotemporal concentration distribution of a PET radiotracer (3D+t) in the course of the process, with a resolution of ~1 mm and tracer sensitivity to some ten thousand atoms per 1 mm³ voxel. Our PET data sets are typically complemented by μCT-images. We demonstrated its advantages for elucidating heterogeneous processes on different time scales, conservative and reactive flow experiments, including the transport of nano-particles. We considered our 3D+t data sets as highly valuable for benchmarking of reactive transport modelling results. In the recent past we have consequently gained some experiences in aligning differently complex data sets (up to 3D, (non-)reactive) with available modelling tools. As suitable for aligning our data with well-established transport codes we identified Comsol Multiphysics for the transport process parameter estimation, PhreeqC for the geochemical reaction simulation, as well as couplings of both for reactive transport processes in 2D at the mm to cm scale. Benchmarks in 3D+t have their strength in emphasising on the role of heterogeneity on macroscopic reaction rates. Here, retroactions from geochemical reactions on the effective transport pathways in geological media (dissolution, precipitation, filtration, etc.) cause spatial and temporal variations of their transport properties - processes verifiable by our non-destructive PET method.
We aim at developing into this highest complexity level of reactive transport benchmarking; the backcoupling of reaction on structural transport parameter values (porosity, permeability).
REFERENCES
[1] Kulenkampff, J. et al., 2013. Application of high-resolution positron-emission-tomography for quantitative spatiotemporal process monitoring in dense material. 7. World Congress on Industrial Process Tomography, Krakow, Poland, http://www.isipt.org/worldcongress/7/902.html (free access after registration)

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)

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.

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.

The demand of highly efficient transparent electrodes without the use of rare earth materials such as indium requires a new generation of thin metallic films with both high transparency and electrical conductivity. For this purpose, Direct Laser interference Patterning was used to fabricate periodic hole-like surface patterns on thin metallic films in order to improve their optical transparency by selective laser ablation of the material and at the same time keeping the electrical properties at an acceptable level.
Metallic films consisting of aluminum and copper with film thicknesses ranging between 5 and 40 nm were deposited on glass substrates and treated with nanosecond and picosecond pulse laser system..In order to analyze the processability of the films, the laser ablation threshold for each material as function of the layer thickness and pulse duration was firstly determined. After analyzing these initial experiments, the samples were structured with a 1.7 μm spatial period hole-like-pattern using three beam direct laser interference patterning. The structural quality of the fabricated structures was analyzed as function laser energy density (laser fluence) using scanning electron microscopy (SEM), atom force microscopy (AFM). Finally, optical and electrical properties of the films were characterized using optical spectroscopy, as well as surface impedance measurements.

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.

Pulsed radiation fields, characterized by microsecond pulse duration and correspondingly high pulse dose rates, are increasingly used in therapeutic, diagnostic and research applications. Yet, dose rate meters which are used to monitor radiation protection areas or to inspect radiation shielding are mostly designed, characterized and tested for continuous fields and show severe deficiencies in highly pulsed fields. Despite general awareness of the problem, knowledge of the specific limitations of individual instruments is very limited, complicating reliable measurements. We present here the results of testing three commercial dose rate meters, the RamION ionization chamber, the LB 1236-H proportional counter and the 6150AD-b scintillation counter, for their response in pulsed radiation fields of varied pulse dose and duration. Of these three the RamION proved reliable, operating in a pulsed radiation field within its specifications, while the other two instruments were only able to measure very limited pulse doses and pulse dose rates reliably.

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.

Laserbasierte Partikeltherapie.

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.

The electronic transport properties of insulating Si:Ga films with superconducting, Ga-rich nanopreciptates are investigated in dependence on temperature, current, and magnetic field. The large negative magnetoresistance, observed below the critical temperature, can be explained by Cooper pair breaking and subsequent tunneling of the fermionic quasiparticles. Localization due to quantum interferences of bosons or fermions, as recently discussed, seems not to be the reason for the insulating state and the large magnetoresistance. Cooper pair tunneling is blocked by the high Coulomb barrier. The quasiparticles can overcome the barrier by inelastic cotunneling that results in nonlinear current-voltage characteristics and negative electroresistance. Since the experimental results obtained for the Si:Ga film resemble that of many other films with superconducting nanoprecipitates the conclusions drawn here could be quite general.

The long-term goal to integrate laser-based particle accelerators into radiotherapy clinics not only requires technological development of high-intensity lasers and new techniques for beam detection and dose delivery, but also characterization of the biological consequences of this new particle beam quality, i.e. ultra-short, ultra-intense pulses. In the present work, we describe successful in vivo experiments with laser-driven electron pulses by utilization of a small tumour model on the mouse ear for the human squamous cell carcinoma model FaDu. The already established in vitro irradiation technology at the laser system JETI was further enhanced for 3D tumour irradiation in vivo in terms of beam transport, beam monitoring, dose delivery and dosimetry in order to precisely apply a prescribed dose to each tumour in full-scale radiobiological experiments. Tumour growth delay was determined after irradiation with doses of 3 and 6 Gy by laser-accelerated electrons. Reference irradiation was performed with continuous electron beams at a clinical linear accelerator in order to both validate the dedicated dosimetry employed for laser-accelerated JETI electrons and above all review the biological results. No significant difference in radiation-induced tumour growth delay was revealed for the two investigated electron beams. These data provide evidence that the ultra-high dose rate generated by laser acceleration does not impact the biological effectiveness of the particles.

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.

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.

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.

The crystal structure of the trisodium uranate, which forms following the interaction between sodium and hyperstoichiometric urania, has been solved for the first time using powder X-ray and neutron diffraction, X-ray Absorption Near-Edge Structure spectroscopy, and solid state 23Na Multi-Quantum Magic Angle Spinning Nuclear Magnetic Resonance. The compound, isostructural with Na3BiO4, has a monoclinic symmetry, in space group P2~c. Moreover, it has been shown that this structure can accommodate some cationic disorder, with up to 16(2)% sodium on the uranium site, corresponding to the composition -Na3(U1−x,Nax)O4 (0

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).

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.

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.

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.

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.

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.

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.

keines Vorhanden

keines vorhanden.

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.

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.

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.

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.

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.

In III-V nanowires the energetic barriers for nucleation in zinc blende or wurtzite arrangement are typically of similar order of magnitude. As a result, both arrangements can occur in a single wire. Here, we investigate the evolution of this polytypism in self-catalyzed GaAs nanowires on Si(111) grown by molecular beam epitaxy with time-resolved in situ X-ray diffraction. We interpret our data in the framework of a height dependent Markov model for the stacking in the nanowires. This way, we extract the mean sizes of faultless wurtzite and zinc blende segments -- a key parameter of polytypic nanowires -- and their temporal evolution during growth. Thereby, we infer quantitative information on the differences of the nucleation barriers including their evolution without requiring a model of the nucleus.

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.

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.

We report on the fabrication, optical properties and lasing characteristics of Yb-doped fused silica in bulk volume. The glass rods were manufactured by sintering of Yb-doped fused silica granulates and subsequent homogenization. Samples of various thicknesses containing doping levels of 0.27 mol% and 0.39 mol%, respectively, were investigated. The glass shows a high optical quality with refractive index variations in the 10 ppm range. We successfully demonstrated cw lasing with a maximum optical to optical efficiency of 60 % and slope efficiencies of about 70 % with respect to absorbed pump power for all samples. The laser cavity could be tuned in a wavelength range of 100 nm. The large amplification bandwidth of fused silica was verified by gain distribution measurements in a double-pass amplifier configuration.

POD modes and coefficients obtained from an inclined flat plate with Lorentz force actuator are compared to that of a pitching wing model (NACA 0009). The pitching wing model emulates an impulsive disturbance by pitching from 15 deg to 17 deg and then back to 15 deg in a very short time interval. There is also a negative pitching case, 15 deg to 13 then back to 15 deg. The Lorentz force actuator produced a spatially localized disturbance, whereas the pitching wing produces a spatially global disturbance. We found very close similarities in the POD modes and the time-varying coefficients. We also found that POD mode 2 tracks the negative of the lift force in both cases.

The field-induced ordering transition in the quantum spin system NiCl₂ · 4SC(NH₂)₂ is studied by means of neutron diffraction, ac magnetometry, and relaxation calorimetry. The interpretation of the data is strongly influenced by a finite distribution of transition fields in the samples, which was present but disregarded in previous studies. Taking this effect into account, we find that the order-parameter critical exponent is inconsistent with the BEC universality class even at temperatures below 100 mK. All results are discussed in comparison with previous measurements and with recent similar studies of disordered Ni(Cl_1−xBr_x)₂ · 4SC(NH₂)₂.

We report detailed ⁷⁵As nuclear quadrupole resonance investigations of the locally noncentrosymmetric superconductor SrPtAs. The spin-lattice relaxation studies prove weakly coupled multigap superconductivity. A retardation of the decay in 1/T₁T evidences a nodeless (fully gapped) superconducting state on the complex multipocket Fermi surface, which is consistent with an anisotropic s-wave order parameter and with proposed unconventional f-wave and chiral d-wave symmetries. A quantitative analysis of these models favors the unconventional f-wave state.

Spin torque from spin current applied to a nanoscale region of a ferromagnet can act as negative magnetic damping and thereby excite self-oscillations of its magnetization. In contrast, spin torque uniformly applied to the magnetization of an extended ferromagnetic film does not generate self-oscillatory magnetic dynamics but leads to reduction of the saturation magnetization. Here we report studies of the effect of spin torque on a system of intermediate dimensionality—a ferromagnetic nanowire. We observe coherent self-oscillations of magnetization in a ferromagnetic nanowire serving as the active region of a spin torque oscillator driven by spin orbit torques. Our work demonstrates that magnetization selfoscillations can be excited in a one-dimensional magnetic system and that dimensions of the active region of spin torque oscillators can be extended beyond the nanometre length scale.

Donor-acceptor (DA) polymers have been found to be good materials for organic electronics since they provide interesting features like mechanical flexibility and high impact resistance.
Moreover, they offer the possibility to produce devises by low cost roll-to-roll printing techniques.
Thus, they are highly promising candidates for organic thin-film transistors and solar cells.
For applications, however, these materials should fulfill several demands such as ambient stability, good solubility, and good film-forming properties.
The charge carrier mobility is one of the most important quantities.
In order to analyse the influence of the molecular structure on these properties, we investigate DA polymers using first-principals methods as density functional theory (DFT).
In particular, density functional based tight binding (DFTB) is used to study large systems.

In our study we analyse the electronic structures of the isolated monomers which are the building blocks of the DA polymers, of finite oligomers up to a length of 20 conjugated units, and of infinite long polymers using periodic boundary conditions.
Furthermore, we investigate the morphological properties by studying systems of several polymer chains with different crossing angles and relative shifts.

Using Marcus transfer theory, we then calculated the electronic transport properties based on hopping processes.
Here, we focus on the coupling matrix elements and their dependence on the stacking configuration.
Using a Boltzmann-like approach for evaluating an average value of this quantity, we obtain good agreements to experimental trends.
Especially the dominating transport type is nicely reproduced by our approach.

no abstract submitted