Physikalisches Kolloquium

Vorträge im SS 2014

Physikalisches Kolloquium der Universität Kiel

 

Dienstag, 29. Apr. 2014 - Prof. K. Meier, KIP Universität Heidelberg

From Ions to Electrons - Physical Models of Brain Circuits

Dienstag, 06. Mai 2014 - Prof. B. Abel, IOM Leipzig / U Leipzig

Ultrafast spectroscopy near liquid water interfaces employing high-harmonics radiation

Dienstag, 13. Mai 2014 - Frau Dr. Tanja Mehlstäubler, Physik. Techn. Bundesanstalt

Relativistic Geodesy with Optical Clock

Dienstag, 27. Mai 2014 - Dr. Julia Stähler, F.-Haber-Institut Berlin

Ultrafast dynamics of exciton formation at the ZnO (10-10) surface

Dienstag, 03. Jun. 2014 - Prof. G. Brezesinski, MPI Potsdam

Amphilic molecules confined at the air / liquid interface

Montag, 16. Jun. 2014 (Sonderkolloqium) - Dr. Dieter Bilitza, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA und George Mason University, Space Weather Laboratory, Fairfax, Virginia, USA

Die Ionosphäre - Einführung und neueste Ergebnisse

Dienstag, 24. Jun. 2014 - Dr. D. Lundin

Thin film deposition by plasma-based processes

Dienstag, 01. Jul. 2014 - Dr. Birger Buttenschön, Max-Planck-Institut für Plasmaphysik, Greifswald

Plasma Wakefield Acceleration - Ein neues Beschleunigerkonzept zur Erzeugung hochenergetischer Elektronen- und Positronenstrahlen

Dienstag, 08. Jul. 2014 - Dr. Klaus Ellmer, Helmholtz-Zentrum Berlin

Großflächiges Magnetronsputtern von Solarzellen und Wasserspaltungselektroden für zukünftige regenerative Energieversorgung

Vorträge im WS 2016/2017

Kolloquiumsvorträge (dienstags, 12.15 Max-Planck Hörsaal)

  • 18. Oktober

    Bridget Murphy (IEAP)  Murphy.pdf
    When (two) surfaces meet
     
  • 25. Oktober 2016

    Rodger Thomson (Tucson)  Thompson.pdf
    Testing Dark Energy and New Physics with Fundamental Constants
     
  • 15. November 2016

    Hanno Kählert (ITAP) Kählert.pdf
    Challenges for theory in strongly coupled (complex) plasmas

     
  • 13. Dezember 2016

    Alexey Chernikov (Univ. Regensburg)
    Excitons in 2D materials

    Since the discovery of graphene, a single sheet of carbon atoms, research focused on two-dimensional (2D) van der Waals materials evolved rapidly due the availability of atomically thin, thermally stable crystals with intriguing physical properties. The 2D materials naturally inherit major traits associated with systems of reduced dimensionality: strongly enhanced interactions, efficient light-matter coupling, and sensitivity to the environment. In particular, the considerable strength of the Coulomb forces, i.e., electrical attraction and repulsion between the charge carriers, introduces a rich variety of many-body phenomena. It leads to the emergence of atom-like electron-hole quasi-particles, such as excitons, trions, and biexcitons, with unusually high binding energies and efficient light absorption.

     

    In this talk, I will focus on the physics of excitons in semiconducting 2D materials, largely determining the optical response of these ultra-thin layers. The observation of exciton binding energies on the order of many 100’s of meV and the marked deviation of the electron-hole attraction from the conventional Coulomb law will be discussed. The results reflect both strong carrier confinement and the distinctive nature of the dielectric screening in atomically thin systems. I will further describe how some of the more extreme non-equilibrium conditions such as strong photo-excitation and high electrical doping can profoundly alter the many-body interactions.



  • 17. Januar 2017

    Karl Jakobs (Uni Freiburg)

    From the Discovery of the Higgs Boson to the Search for Dark Matter

    -New results from the LHC-

     

    With the discovery of the Higgs boson by the two large experiments ATLAS and CMS at the Large Hadron Collider (LHC) at the European laboratory for particle physics CERN in Geneva, an important milestone in the investigation of the fundamental interactions was reached. Despite this discovery important questions remain open: does the discovered particle have the properties as predicted by the Brout-Englert-Higgs mechanism in the Standard Model or does it show devi­ations pointing to new physics? Are there new symmetries and -linked to them- new particles that could explain the Dark Matter in the Universe?

     

    In June 2015 a new data-taking period has started and proton-proton collisions are investi­gated with an energy of 13 TeV –nearly twice the collision energy used in the previous years. A new energy window opens up where the above-mentioned questions can be addressed. In the talk, the current status of the measurements at the LHC is presented. In particular, the properties of the discovered Higgs boson and the search for candidate Dark Matter particles are discussed.

     


     
  • 24. Januar 2017

    Angel Rubio (Max Planck Institute for the Structure and Dynamics of Matter, Hamburg)

    Modeling Light-Matter interaction: From Weak to Strong Coupling in QED Chemistry and Materials

    Computer simulations that predict the light-induced change in the physical and chemical properties of complex systems, molecules, nanostructures and solids usually ignore the quantum nature of light.  We have recently shown how the effects of the photons can be properly included in such calculations.  The basic idea is to treat the full QED system of particles and photons as a quantum fluid. Here the particles are represented by a charge current, and the photons by a classical electromagnetic field that acts on the current in a very complex manner.  This study opens up the possibility to predict and control the change of material properties due to the interaction with light particles from first principles .
     
    Here we will review the recent advances within density-functional a schemes to describe spectroscopic properties of complex systems with special emphasis to modeling  time and spatially resolved electron spectroscopies   We will discuss the theoretical approaches developed in the group  for  the characterization of matter out of equilibrium, the control material processes at the electronic level and tailor material properties, and  master energy and information on the nanoscale to propose new devices with capabilities. We will focus on examples  linked to the efficient conversion of light into electricity or chemical fuels ("artificial photosynthesis") and the design on new nanostructure based optoelectronic devices, among others.  
     
    Our  goal is to provide a detailed, efficient, and at the same time accurate microscopic approach for the ab-initio description and control of the dynamics of decoherence and dissipation in quantum many-body systems. This theoretical framework provides a new way to control and alter chemical reactions in complex systems,  direct the movement of electrons, selectively trigger physico-chemical processes, and create new state of matter.

 

  • 31. Januar 2017

    Axel Gross (Uni Ulm)
    Challenges in the theoretical description of electrochemical energy storage and conversion

    In spite of its technological relevance in the energy conversion and storage, our knowledge about the microscopic structure of electrochemical electrode-electrolyte interfaces and electrical double layers is still rather limited. The theoretical description of these interfaces from first principles is hampered by three facts. i) In electrochemistry, structures and properties of the electrodeelectrolyteinterfaces are governed by the electrode potential which adds considerable complexity to the theoretical treatment since charged surfaces have to be considered. ii) The theoretical
    treatment of processes at solid-liquid interfaces includes a proper description of the liquid which requires to determine free energies instead of just total energies. This means that computationally expensive statistical averages have to be performed. iii) Electronic structure methods based on
    density functional theory (DFT) combine numerical efficiency with a satisfactory accuracy. However, there are severe shortcomings of the DFT description of liquids, in particular water, using current functionals.

    Despite these obstacles, there has already significant progress been made in the first-principles modeling of electrochemical electrode-electrolyte interfaces. In this contribution, I will present our attempts to contribute to this progress by systematically increasing the complexity of the considered systems [1]. Different approaches to describe aqueous electrolytes at electrodes using first-principles calculations will be compared: the electrolyte can be described either as a thermodynamic reservoir or using implicit of explicit solvent models [2,3]. The equilibrium coverage of specifically adsorbed anions such as halides will be addressed which is an integral part of the realistic modeling of electrochemical double layers [2]. Furthermore, the modelling of electrocatalytic reactions occurring in fuel cells [3] will be presented. Finally, first attempts to model
    structures and processes in batteries using electronic structure calculations will be presented.

    [1] N. Hörmann, M. Jaeckle, F. Gossenberger, T. Roman, K. Forster-Tonigold, M. Naderian, S. Sakong, and A. Groß, Some challenges in the first-principles modeling of structures and processes in electrochemical energy storage and transfer, J. Power Sources 275, 531-538 (2015).

    [2] F. Gossenberger, T. Roman and A. Groß , Hydrogen and halide co-adsorption on Pt(111) in an electrochemical environment: a computational perspective, Electrochim. Acta 216, 152-159 (2016).

    [3] S. Sakong and Axel Groß, The importance of the electrochemical environment in the electrooxidation of methanol on Pt(111), ACS Catal. 6, 5575 (2016).
     
  • 07. Februar 2017

    Ronald Redmer (Universität Rostock)
    Warm Dense Matter - Probing Planetary Interiors

    The behaviour of warm dense matter (pressures up to the TPa region and temperatures up to several eV) is of paramount importance for understanding the interior, evolution and magnetic field of solar and extrasolar planets. While the light elements H and He are the main components of gas giants like Jupiter, mixtures of H-He-C-N-O are relevant for Neptune-like planets, and minerals of the MgO-FeO-SiO2 complex are the building blocks of rocky planets (Earth, super-Earths). The high-pressure phase diagram of these elements and mixtures has to be known in order to develop corresponding models. Of special interest in this context is the location of the melting line, of potential regions of phase separation and metal-insulator transitions. These high-pressure phenomena have a strong impact on interior, evolution, and dynamo models for planets and, simultaneously, constitute a major challenge to plasma and computational physics. 
    Molecular dynamics simulations based on finite-temperature density functional theory are used to predict the equation of state, the high-pressure phase diagram, and the transport properties of warm dense matter for a wide range of densities and temperatures as typical for the interior of planets. These data are benchmarked against diamond-anvil-cell and shock-wave experiments and then applied to construct interior and evolution models for solar and extrasolar planets.

     
  • 25. April 2017

    Hans Böhringer (Max-Planck-Institut für Extraterrestrischer Physik)

     
  • 16. Mai 2017

    Jürgen Blum (TU Braunschweig)
    Die Entstehung der Planetesimale im jungen Sonnensystem

     
  • 30. Mai 2017

    Claus Lämmerzahl (ZARM, Univ. Bremen)
    Quantenmechanik und Gravitation
     
  • 18. Juli 2017

    Reserviert (A. Piel)

     

 

Vorträge im SS 2017

Kolloquiumsvorträge (dienstags, 16.15 Hans-Geiger Hörsaal)

 

  • 18. April 2017

    Hans Böhringer (Max-Planck-Institut für Extraterrestrische Physik)

    Erforschung der Struktur unseres Universums mit Hilfe von Galaxienhaufen im Röntgenlicht

    Galaxienhaufen als größte klar definierte Objekte in unserem Universum sind ideale Testobjekte zur Vermessung der großräumigen, kosmischen
    Struktur und zum Test kosmologischer Modelle. Durch das mehrere 10 Millionen Grad heiße Plasma, das die Haufen ausfüllt, erscheinen die Haufen als besonders interessante Objekte in der Röntgenastronomie. Röntgenbeobachtungen bieten daher einen besonders guten Zugang zur Charakterisierung und zum Verständnis dieser Systeme.

    Aus dem Himmelsatlas im Röntgenbereich, der mit dem deutschen Röntgensatelliten ROSAT erstellt wurde, haben wir den größten Katalog röntgenleuchtender Galaxienhaufen ertellt und die Struktur von Stichproben dieser Haufen im Detail untersucht. Tests kosmologischer Modelle mit Hilfe dieser Daten liefern z.B. einen Wert für die mittlere Materiedichte unseres Universums.
    Das Ergebnis zeigt, dass wir zur Erklärung der Beobachtungen eine bisher unbekannte "Dunkle Materie" brauchen, und dass möglicherweise ein
    kleinerer Teil dieser Materie aus Neutrinos mit endlicher Restmasse besteht. Beim Studium der Materieverteilung im nahen Universum stellen wir fest, dass wir uns in einer Umgebungen mit weniger als mittlerer Materiedichte befinden, mit wichtiger Auswirkung auf die lokale Hubble Konstante im Vergleich zu ihrem globalen Wert.
     

  • 2. Mai 2017

    Thomas Frauenheim (Uni Bremen)
    Multi-scale modeling of nanostructured devices

    Presently electronic and optoelectronic devices scale down to nanometer sizes at which quantum atomistic modeling can be used to understand the fundamental mechanisms and optimize quality and performance. In this talk I am going to describe recent developments of DFTB-based atomistic and charge transport simulations addressing applications to ultra-scaled Silicon-on-Oxide electronic devices and nanostructured solar cells and light emitting diodes.

    (1) Ultimate scaling of Si MOSFETs leads to extremely thin and short channels, which are justifiably modeled at the atomic level. Currently, hydrogen-termination of the channel is used in device models, as a compromise between efficiency and accuracy. This work advances the state of the art by adopting a density-functional tight-binding (DFTB) Hamiltonian, permitting the inclusion of the confining oxide explicitly in the simulation domain in an ab initio fashion. Simulations of band-structure and electron transport in extremely thin SOI MOSFET are studied with this method, showing good agreement with experiment and reveal a large quantitative difference when compared to simulations with H-passivated channel. S. Markov et al. IEEE Transaction on Electron Devices 62 (2015) 696.

    (2) simulations of photovoltaic devices are based on classical models, which neglect the atomistic details and quantum-mechanical effects besides the dependence on many empirical parameters. Within the nonequilibrium Green’ s function formalism, we present a quantum-mechanical study of the performance of inorganic nanowire-based photovoltaic devices. On the basis of density-functional tight-binding theory, the method allows simulation of current− voltage characteristics and optical properties of photovoltaic devices without relying on empirical parameters. Numerical studies of silicon nanowire-based devices of realistic sizes with 10 000 atoms are performed, and the results indicate that atomistic details and nonequilibrium conditions have a clear impact on the photoresponse of the devices. Y. Zhang, et al. Journal of Ohys. Chem. Letters, 5 (2014) 1272.

    (3) Understanding of the electroluminescence (EL) mechanism in optoelectronic devices is imperative for further optimization of their efficiency and effectiveness. Here, a quantum mechanical approach is formulated for modeling the EL processes in nanoscale light emitting diodes (LED). Based on non-equilibrium Green’s function quantum transport equations, interactions with the electromagnetic vacuum environment are included to describe electrically driven light emission in the devices. The presented framework is illustrated by numerical simulations of a silicon nanowire LED device. EL spectra of the nanowire device under different bias voltages are obtained and, more importantly, the radiation pattern and polarization of optical emission can be determined using the current approach. This work is an important step forward towards atomistic quantum mechanical modeling of the electrically induced optical response in nanoscale systems. R. Wang, et al. Nanoscale ( (2016) 13168.

    If time allows, I will report on the time-dependant DFTB implementations and describe recent applications to nitric oxide degradation on titania surfaces and hot electron injection into TiO2 nanoparticles.
     

  • 16. Mai 2017

    Jürgen Blum (IGeP, TU Braunschweig)
    Die Entstehung der Planetesimale im jungen Sonnensystem
     

    Unser Wissen über die Entstehung der Planeten ist immer noch lückenhaft. Aus astronomischen Beaboachtungen können wir lernen, dass Planeten in so genannten protoplanetaren Scheiben entstehen, die zu 99% aus Gas und zu 1% aus mikroskopisch kleinen Staubpartikeln bestehen. In diesen Scheiben kollidieren die Staubteilchen, haften aneinander und bilden bis zu zentimetergroße Agglomerate. Dies konnte durch Modellierung, 
    Labormessungen und astronomische Untersuchungen bestätigt werden. Das weitere Wachstum hin zu Planetesimalen, den kleinsten gravitativ 
    gebundenen Körpern mit Durchmessern von einigen Kilometern, wird zurzeit noch kontrovers diskutiert. Die beiden favorisierten Modelle 
    unterscheiden sich darin, dass im einen das Wachstum aufgrund haftender Stöße fortschreitet, im anderen hingegen eine hydrodynamische 
    Instabilität in der protoplanetaren Scheibe, die "Streaming Instability", für eine so starke Konzentration der zentimetergroßen Staubklumpen sorgt, dass der gesamte Komplex gravitativ kollabiert.
    Mit der jüngst abgeschlossenen Mission Rosetta zum Kometen 67P/Tschurjumow-Gerassimenko konnte erstmals ein Körper aus den Frühzeiten des Sonnensystems im Detail untersucht werden. Die bislang vorliegenden Ergebnisse deuten darauf hin, dass Komet 67P durch einen gravitativen Kollaps in seiner heutigen Form entstanden ist. Wenn sich dies bestätigen sollte, liegt der Schluss nahe, dass Planetesimale nicht durch haftende Stöße, sondern durch Instabilitäten in protoplanetaren Scheiben entstehen.
     

  • 13. Juni 2017,
    Beginn 17.15Uhr (!)


    Tiberiu Minea (U Paris-Sud, Frankreich)
    Modeling of vacuum breakdown. Thermo-field, dynamics of microparticles and laser assisted electron emission


    Vacuum is often used as an isolator in numerous applications, such as X-ray tubes, particle accelerators, high voltage pass-through, etc. However, their performance is limited by the risk of unpredictable breakdown events between electrodes. Moreover, the breakdown usually leads to the formation of arc discharges, which can seriously damage the system.

    Since 2010 the LPGP develops a research program “High Voltage holding In Vacuum”, in collaboration with CEA and CentraleSupelec which aims to give a better description of the origin of the vacuum breakdown.


    Three numerical models have been developed to tackles three particular aspects of the problem.


    (i) The model OVIP (Orsay Vacuum Insulation Percolation) deals with the thermos-field electron emission from a surface microprotrusion and the results are in good agreement with the experimental results for breakdown. The operation with fast pulses allows to enhance the field emission avoiding the breakdown.

    (ii) The model OFEN (Orsay Field Emission Nanoparticles) describes the micro-particles (MP) transport in the inter-electrodes gap, in vacuum) and the interactions (heating and modification of the MP charge) between electrons and the MP. It is an extension of the Cranberg’s theory of clumps when the MP is exposed to an intense field ~1-5 MV/m and it is simultaneous bombarded by electrons released from the cathode micro-tips. The results clearly show four different regimes of MP trajectories obtained for different emission currents, MP sizes and inter-electrode distances and the effect of the MP crash of on the cathode, helping to understand the vacuum conditioning.

    (iii) The last model OFELIE (Orsay Field Emission and Light Emission) analysis the electron emission induced by picosecond laser from solid surfaces placed under an intense electric field. The results show an important difference between the electrons temperature (5500 K) and the phonons temperature (850 K). In these conditions, the Fermi-Dirac distribution depends of the electron temperature, while the thermo-field emission becomes effective for temperatures well below the fusion of the metal.

    In conclusion, the modeling of the related phenomena between solid and vacuum depends on the way the energy is transferred to the electrons and it helps to distinguish between different scenarios and to design performant systems.
     
  • 04. Juli 2017

    Eberhard Möbius (Space Science Center and Department of Physics, University of New Hampshire)

    Astronomy with Neutral Atoms - Imaging the Heliospheric Boundary and Catching the Interstellar Wind with the Interstellar Boundary Explorer

    400 years after Galileo pointed a telescope at celestial objects for the first time, neutral atoms were added to the astronomical toolbox with the Interstellar Boundary Explorer (IBEX), launched October 19, 2008. Since early 2009, two energetic neutral atom (ENA) cameras take global images of the solar system’s interaction with its galactic neighborhood. They have returned stunning images of the heliospheric boundary region, where the solar wind slows down in response to the surrounding interstellar medium, including the front and tail region of the heliosphere. Most unexpectedly, the images show a bright and persistent “Ribbon” across the sky, which provides a marker for the direction of the local interstellar magnetic field, but the processes leading to the bright ENA emission are still being investigated. Time variations in the ENA fluxes that vary with energy provide additional constraints and point to the neutral solar wind that penetrates beyond the boundary of the heliosphere. The IBEX-Lo camera catches the interstellar wind of neutral H, He, O, and Ne atoms that blows through the solar system with a speed of ≈26 km/s and arises from the motion of the Sun relative to the surrounding local interstellar gas cloud (LIC). This observed gas flow distribution is an excellent probe of the state of the LIC and shows clear signatures of the deflection of the interstellar plasma at the heliospheric boundary.


     
  • 11. Juli 2017

    Erwin O. Flückiger
    60 Jahre Neutronenmonitor

     
  • 18. Juli 2017, 15:00 Uhr

    Abschiedskolloquium von Prof. Piel

 

Vorträge im WS 2017/2018

  • 24.10.2017

    Dr. Gerard van Rooij (Dutch Institute for Fundamental Energy Research DIFFER, Eindhoven) abstract
    Electrification of chemical industry: a key role for plasma chemistry

    Sustainable energy generation by means of wind or from solar radiation through photovoltaics or concentrated solar power will continue to increase its share of the energy mix. Intermittency due to e.g. day/night cycle, regional variation in availability, and penetration of sustainable energy into sectors other than electricity such as the chemical industry necessitates means of storage, transport and energy conversion on a large scale. A promising option is the synthesis of chemicals and artificial fuels using sustainable energy. A truly circular economy requires that the raw materials are the thermodynamically most stable ones such as CO_2 and N_2 . In this contribution it will be highlighted how plasma chemistry can potentially combine compatibility with e.g. intermittency and localized production to activate these molecules with maximum energy efficiency, essentially due to preferential vibrational excitation (causing inherently strong out-of-equilibrium processing conditions that achieve selectivity in the reaction processes). Examples will be discussed of research carried out at DIFFER to ultimately enable a scale up to chemical industrial applications.

 

  • 07.11.2017

    Dr. Volker Schulz-von der Gathen (Fakultät für Pysik und Astronomie der Ruhr-Universität Bochum)
    Microplasma arrays: Concept, configuration, characteristics and potential applications

 

Der Vortrag von Dr. Schulz-von der Gathen am 07. November fällt auf Grund von Krankheit leider aus! Der Neue Termin wurde für die 09.01.2018 festgelegt.
 
  • 21.11.2017

    Dr. Michael Klick (Plasmatrex, Berlin) abstract
    Zur Plasma-Wand-Wechselwirkung in industriellen HF-Plasmen​

    Die Plasma-Wand-Wechselwirkung ist für die industrielle Nutzung von chemisch aktiven HF-Plasmen von fundamentaler Bedeutung. Im Bereich des Plasma-Ätzens in der Halbleiter-Industrie ist die sogenannte Konditionierung von Prozesskammern nach einer Reinigung im Abstand von einigen Wochen oder Monaten Vorbedingung für die Freigabe zur Fertigung. Dies trifft aber auch für PECVD-Kammern im laufen-den Betrieb zu, da die auch auf der Wand abgeschiedene Schicht i.a. wieder zurück geätzt werden muss. [mehr im abstract]

  • 28.11.2017

    Prof. Dr. Claus Lämmerzahl (ZARM, Bremen) abstract
    An operational foundation of General Relativity and the search for Quantum Gravity

    General Relativity seems to be incompatible with the principles of quan-tum theory. Therefore, a new theory - Quantum Gravity - is expected to replace General Relativity which also should lead to new physical effects. However, no finally worked out Quantum Gravity theory exists. In order to be able to already design experiments searching for expected effects of Quantum Gravity one has to carry out such experiments which give a foundation of General Relativity. Such a program is described in this talk: Based on an constructive axiomatic approach to General Relativity from Ehlers, Pirani, and Schild experiments are described which have the poten-tial to find deviations from standard physics related to Quantum Gravity.

  • 12.12.2017

    Prof. Dr. Peter Schmelcher (Universität Hamburg) abstract
    Mesoscopic Physics with Ultracold Atoms: From Few- to Many-Body Systems

    Bose-Einstein condensates, matter waves and generally ultracold atomic physics have seen over the past two decades a breathtaking development and represent nowadays an important part of modern quantum physics. We provide here an overview of me-soscopic aspects of ultracold atomic structures and processes in tightly confining traps. For strongly interacting ultracold atoms novel tunneling mechanisms occur which play a key role for the atomic transport and the formation of rich quantum pha-ses. We demonstrate a variety of tunneling processes which are the basis of the emerging field of atomtronics, some of them being counterintuitive, such as the tun-neling of repulsively bound atomic clusters.
    A special focus will be on the none-quilibrium quantum dynamics of ultracold bosonic and fermionic ensembles where correlations determine the response due to a quantum quench or a continuous driving. Recent methodological developments allow to explore the correlated dynamics in the crossover regime from few- to many-body systems in order to understand the emergence of collective behaviour.

  • 19.12.2017

    Dr. Kählert (Reserviert)

  • 09.01.2018

    Dr. Volker Schulz-von der Gathen (Fakultät für Pysik und Astronomie der Ruhr-Universität Bochum) abstract
    Microplasma arrays: Concept, configuration, characteristics and potential applications

    Microplasma arrays belong to the class of low temperature non-equilibrium atmospheric pressure plasma devices. They consist of huge numbers of about 100 micrometer size cavities regularly positioned on a common ground. These structures are usually generally manufactured applying microstructure techniques on silica wafers [1], but other configurations have been investigated recently. Being basically dielectric barrier discharges, the devices are typically driven by a single power supply at kHz frequencies at voltages of a few hundred volts. Due to the small dimensions strong fields exist in close contact with the surfaces that introduces new physical features. The geometric configuration results e.g. in unique features of discharge dynamics as ionization waves. A huge number of possible applications have been proposed over the last years [2]. The examples range from photonic applications as light generation and detection to large scale surface treatments or use as meta materials. In this talk we will give a basic description of the concepts of microplasma arrays, their operation and some application possibilities. Subsequently we will describe some of the physical features observed mainly by analysis of optical emission.

    [1] J.G. Eden, S.-J. Park, and K.-S. Kim, „Arrays of non-equilibrium plasmas confined to microcavities: an emerging frontier in plasma science and its applications“ Plasma Sources Science and Technology, 2006, 15, S67-S73
    [2] J.G. Eden, and S.-J. Park, „Microcavity plasma devices and arrays: a new realm of plasma physics and photonic applications“, Plasma Phys Control Fusion, 2005, 47, B83-B92

  • 16.01.2018

    Prof. Dr. Ulrich Stroth (TU München/IPP) abstract
    Über die zentrale Bedeutung des Plasmarandes für die Fusionsforschung

    Der Votrag beschreibt die physikalischen Prozesse, die den Rand des Fusionsplasmas auszeichnen, wo der Übergang vin einem bis zu 100 Millionen Grad heißen Plasma zu den umgebenden matiellen Wänden vollzogen wird. Die Forschung auf diesem Gebiet ist stark interdisziplinär. Sie greift auf Konzepte aus verschiedenen Fachgebieten zurück, angefangen bei der Festkörperphysik, über die Atmo- und Molekülphysik und die Magnetohydrodynamik, bis hin zur Plasmaturbulenz. Durch die Darstellung ausgewählter Prozesse wird das Zusammenwirken der verschiedenen Einflüsse auf das Plasma sichtbar gemacht.
    Das Verständnis des Plasmaranders ist insbesondere dazu notwendig, um eine sichere Leistungabfuhr aus Fusionsplasmen zu gewährleisten. Mögliche Realisierungendes Plasmarandes für ein Fusionskraftwerk werden beispielhaft and den Experimenten des MPI für Plasmaphysik, dem Tokamak ASDEX Upgrade und dem Stellarator Wendelstein 7-X, dargestellt.

  • 23.01.2018

    Prof. Dr. Stefan Kuhr (University of Strathclyde, Glasgow) abstract
    Quantum-Gas Microscopes - Quantum-Simulation with Single-Particle Access

    Ultracold atoms in well-controlled engineered environments in optical lattices are a versa-tile tool for quantum-simulation of strongly correlated quantum systems. The most recent developments in this field include quantum-gas microscopes [1], enabling single-lattice-site resolution and single-atom control [2]. Imaging of with single-atoms resolution has made it possible to directly observe bosonic and fermionic many-body quantum systems in an un-precedented way, giving access to, e.g., in-situ measurements of temperature and entropy distributions, direct observation of correlations and their spreading, or the build-up of en-tanglement. I will present how we achieved single-atom-resolved fluorescence imaging of fermionic potassium-40 atoms using electromagnetically-induced-transparency (EIT) coo-ling [3], and a new way of Raman gray-molasses cooling [4]. I will also report on our pro-gress towards the creation of fermionic Mott insulators and the study of strongly correlated fermionic quantum systems and their out-of-equilibrium dynamics.

  • 30.01.2018

    Prof. Dr. K. Hassouni (Université Paris, France) abstract
    Nanoparticles formation in non-equilibrium plasmas

    Dusty plasmas were observed and investigated since the early 20th century in the context of astrophysical sciences, the early eighties in the context of material processing plasmas and for more than two decades in the context of edge tokamak plasmas and their interaction with fusion reactor materials.
    Surprisingly, the physical mechanisms and collisional processes that lead to the formation of dust particles in plasmas received little attention during the last century. The situation changed with the strong increase of interest for nanomaterial processing and the advent of ITER project. As a matter of fact, dusty plasmas were considered as a promising tool for making and processing functional nanomaterials with unique properties for a variety of applications. On the other hand, the formation of dust particles in tokamak edge plasmas represents a major safety concern and motivated a large research effort with the aim to understand the phys-ical mechanism that lead to the formation of these particles and to propose a way to inhibit these mecha-nisms. (Read more in the attached abstract)

  • 06.02.2018

    Prof. Dr. Livio Narici, INFN (Italian National Institute for Nuclear Physics), Rome abstract
    Anomalous light flashes & other sensory illusions due to charged particles in space and hadrontherapy

    In 1952 an article appeared in Journal of Aviation Medicinehypothesizing the poten-tial hazard of the cosmic rays in spaceflight. Dr. Tobias predicted that individual heavy ions passing through the retina might produce visual effects. In 1969, Edwin Aldrin reported mysterious visual stars and streaks during his lunar mission. This started a still ongoing interest on if and how cosmic radiation could modulate sen-sory and, more at large, brain activity, and if this could represent a functional health hazard. Many researches on ground (especially in the beginning of the 70’s) have been carried on, followed by a smaller number of space experiment (on the Apollo, Skylab, Apollo-Soyuz). More recently the interest revitalized with several investiga-tions both on ground (also on patients undergoing hadrontherapy) and in space. Since Tobias’ prediction we now know that not only heavy ions are producing sen-sory illusions, but also light ions, even protons. And there are also indications that all sensory channels and, possibly, also other brain activities, can be modulated by charged radiation. In this talk a brief history of the light flashes studies followed by a panorama of what is becoming evident about other sensory systems involvement will be presented. Experimental results from the ALTEA program about in vitro and in vivo (on animal models) investigations as well as about studies on humans (pati-ents and astronauts) will be presented.

Vorträge im SS 2018

  • 24.04.2018

    Prof. Dr. Jan Benedikt (CAU IEAP), Kiel abstract
    Kalte Nicht-Gleichgewichts-Plasmen für neuartige Forschung und Anwendungen

    Nicht-Gleichgewichts-Plasmen besitzen vielfältige Anwendungsmöglichkeiten, die vom Satellitenantrieb über die Herstellung von nanostrukturierten Elektronikbautei-len und der Abscheidung von ultraharten Schutzschichten bis hin zur Plasma-Sterilisation oder Plasmatherapie in Medizin reichen. In diesen Plasmen haben nur die Elektronen sehr hohe Temperaturen (mehrere 10.000 Grad), die Schwerteil-chen (Atome, Moleküle, Ionen) bleiben dagegen kalt. Sie sind normalerweise in ei-nem Gas im Niederdruckbereich realisiert, in welchem hauptsächlich die Elektronen durch die elektrischen Felder beschleunigt werden und die Nicht-Gleichgewichtssituation durch eine geringere Stoßfrequenz und Energieübertrag gewährleistet ist. Nicht-Gleichgewichts-Plasmen kann man aber auch bei Atmo-sphärendruck durch gepulste Felder, Begrenzung des Stromes oder Hochfrequenz-felder realisieren. Die energetischen Elektronen führen zur Anregung von Atomen und Dissoziation von Molekülen, was eine Reaktivität des Gases erreicht, die sonst nur bei viel höheren Gastemperaturen stattfinden würde. Darüber hinaus werden Ionen in Richtung Oberfläche beschleunigt und können sehr feine, aber auch sehr tiefe Strukturen ätzen. In diesem Vortrag werden zuerst die Diagnostik der reakti-ven Plasmakomponenten wie Radikale, Ionen oder Vakuum-UV Strahlung disku-tiert und danach die Plasmaanwendungen in multidisziplinären Feldern der Materi-alsynthese oder Plasmamedizin vorgestellt.

  • 08.05.2018

    Prof. Dr. A. Anders (Leibniz Institute of Surface Engineering (IOM), Leipzig) abstract
    Plasma Potential Distribution and Electron Heating in Sputtering Magnetrons

    Sputtering magnetrons are widely used to make thin films and are generally consid-ered a mature technology. Over the last years it has become known that magnetrons show surprisingly rich physics based on plasma instabilities. Without these instabili-ties, magnetrons would generally not work. The energy needed to ionize atoms of the process gas and sputtered from the target is generallythought to be delivered by "hot" secondary electrons (Penning-Thornton paradigm). Recent theoretical [1], spectro-scopic [2], and probe data [3] however indicate that most of the electrons’ energy comes from the presheath, and is provided by localized electric fields concentrated at the edge of "ionization zones" or "spokes" [4, 5]. This is closely related to self-organization and turbulence as observed in interesting images of magnetron plasmas.

  • 15.05.2018

    free - but no accommodation - Special Olympics Deutschland in Kiel

  • 29.05.2018

    Prof. Dr. Ulf Helmersson (Linköping University, Schweden), abstract
    Wires, trusses and pillars produced by assembly of plasma generated nanopartices

    Nanoparticles generated or supplied to a plasma attains a negative potential due to the nature of the plasma. This open up interesting possibilities in synthesis and assembly of the nanoparticles creating structures in the nano- and micro-range. In this work, we use hollow cathode sputtering powered with high-power pulse to ensure close to full ionized of the source material. This promotes rapid growth of the nanoparticles to desired sizes and the negative charge makes it possibility to guide nanoparticles for assembly and collection on desired positions. This is demonstrated by attracting na-noparticles to substrate positions with a positive potential and focusing nanoparticles through a matrix of electrostatic lenses to assemble the nanoparticles into pillars. For ferromagnetic nanoparticles, we also demonstrate generation of nanowires as well as nanowires cross-linked into trusses. Since the iron nanoparticles are generated under relatively pure condition they assemble into wires without oxides in the interfaces. Nanowires and trusses assembled on conducting substrates can potentially be used as low cost large area electrodes.

  • 05.06.2018

    free

  • 12.06.2018

    Prof. Dr. Francis Halzen (Wisconsin IceCube Particle Astrophysics Center and Department of Physics) University of Wisconsin–Madison, abstract
    ICE CUBE and the Discovery of High-Energy Cosmic Neutrinos

    The IceCube project has transformed a cubic kilometer of natural Antarctic ice into a neutrino detector. The instrument detects more than 100,000 neutrinos per year in the GeV to PeV energy range. Among those, we have isolated a flux of high-energy cosmic neutri-nos. I will discuss the instrument, the analysis of the data, the signi-ficance of the discovery of cosmic neutrinos, and the recent multi-messenger observation of a flaring TeV blazar in coincidence with the IceCube neutrino alert IC170922. The large cosmic neutrino flux observed implies that the Universe’s energy density in high-energy neutrinos is the same as that in gamma rays, suggesting that the sources are connected and that a multitude of astronomical objects await discovery.

  • 19.06.2018

    Prof. Dr. Cornelia Denz (Institut für Angewandte Physik) Westfälische Wilhelms-Universität Münster abstract
    Complex light fields for optical manipulation of nanoparticles and cells

    Light can hold, move and measure micro- and nano particle without touching. This allows implementing a device named optical tweezers which exploits focused laser light to trap and manipulate small particles. When using complex tailored light fields based on holographic principles, optical tweezers become an extraordinary metrology tool for analysis in nanophotonics or biophysics.
     

  • 26.06.2018

    Prof. Dr. Thomas Mannel (Universität Siegen, Germany), abstract
    Particle Physics after the Higgs Discovery: Where do we go?

    After the recent discovery of the Higgs boson the so-called Standard Model of particle physics has become a complete and mathematically consistent theory, which – at least in principle – could be valid up to extremely high energies. In this talk I will discuss, why research in particle physics is still well motivated, although the Higgs boson is discovered. I will consider on the one hand the theoretical problems of the standard model, on the other hand, I will discuss experimental hints, why the standard model cannot be the final theory of the fundamental interactions.

  • 03.07.2018
    free

  • 10.07.2018
    free

  • 17.07.2018
    free

Vorträge im WS 2018/2019

  • 30.10.2018

    Dr. Katrin Amann-Winkel (Stockholm University),  abstract - [Magnussen]
    “Does water consist of two liquids? How X-rays reveal water ́s mysteries”

    Water is ubiquitous and the most important liquid for life on earth. Although the water molecule is seemingly simple, various macroscopic properties of water are most anomalous, such as the density maximum at 4°C or the divergence of the heat capacity upon cooling. The fundamental origin of these anomalies is yet to be fully understood [1]. Computersimulations suggest that the anomalous behaviour of ambient and supercooled water could be explained by a two state model of water. An important role in this ongoing debate plays the amorphous forms of water [2]. Since the discovery of two distinct amorphous states of ice with different density (high- and low density amorphous ice, HDA and LDA) it has been discussed whether and how this phenomenon of polyamorphism at high pressures is connected to the occurrence of two distinct liquid phases (HDL and LDL) [3]. X-ray scattering experiments on both supercooled water [4] and amorphous ice [5] are of major importance for our understanding of water. In my talk I will give an overview on our recent experiments on micrometer-sized supercooled water droplets [4] and amorphous ices [5]. Among other techniques, X-ray correlation spectroscopy (XPCS) was used to study the dynamics in amorphous ice around the hypothesized glass transition tempera- ture. Our results are consistent with the hypothesis of a liquid-liquid transition between HDL and LDL [3,4,5].

    [1] Nilsson, A. & Pettersson, L.G.M., The structural origin of anomalous properties of liquid water. 6, 8998, Nature Comms (2015)
    [2] K. Amann-Winkel et al., Water ́s controversial glass transition, Rev. Mod. Phys. 88, 0110002 (2016)
    [3] P. Gallo, K. Amann-Winkel et al., Water: a Tale of Two Liquids, Chem. Rev. 116, 7463-7500 (2016)
    [4] K.H. Kim, A. Spaeh et al., Maxima in the Thermodynamic Response and Correlation Functions of Deeply Supercooled Water, SCIENCE 358, 1589 (2017)
    [5] F. Perakis, K. Amann-Winkel et al., Diffusive dynamics during the high-to-low density transition in amor- phous ice, PNAS 114, 8193 (2017)

  • 06.11.2018
  • 13.11.2018

    Dr. Andreas Dorsel (Zeiss SMT, Oberkochen),  abstract - [Duschl]
    “ZEISS Semiconductor Manufacturing Technology“
    ...where Science meets Industry...

    The advent of Micorelectronics, ubiquitous in all areas of life today, has often been referred to as the third industrial revolution. Semiconductor manufacturing technologies are key in enabling this dramatic development. This talk will try to point to answers questions like
    • Which technologies are key?
    • What are the drivers for these technologies?
    • What are limitations resulting from the laws of physics?
    • What has been achieved and what is considered achievable?
    • What is different when comparing science and academia vs. development and in- dustry
       
  • 20.11.2018
  • 27.11.2018

    Prof. Dr. Andreas Eckart (Universität zu Köln),  abstract - [Duschl]
    The central light-year of the Milky Way
    How stars and gas live in a relativistic
    environment of a super-massive black hole

    The central region of our Milky Way is an extremely active region. It is the closest galactic nucleus that is accessable to us allowing us to study it in fine detail. Here we present most recent results obtained with state of the art instruments providing sensitive measurments at their highest angular resolution. The central star cluster harbors a small cusp of high velocity mostly young and dusty stars that are in orbit around the 4 million solar mass super massive black hole (SMBH) Sagittarius A* (SgrA*). Molecular and atomic gas is streaming towards this region in the form of a spiral connecting it to the Circum Nuclear Ring. Using the Large Atacama Millimeter Array (ALMA) we investigated the kinematics and composition of this material in detail highlighting signatures of star formation and the interaction with a wind emerging form the direction of SgrA*. Using results from the Very Large Telescope (VLT) we will highlight the dynamics of the ultra-fast stars and present theories on their origin. We demonstrate that one of the innermost stars shows clear signs of relativistic motion in the deep potential well of the SMBH. The interaction of plasma with SgrA* reveals that matter is orbiting and is being accreted onto the SMBH to produce powerful flares. These are detectable all across the electromagnetic spectrum and help us to understand the region close to the event horizon of SgrA* which is currently under investigation using the Event Horizon Telescope (EHT).
     
  • 04.12.2018

    Dr. Michael Zeuner (scia systems, Chemnitz), abstract - [Kersten]
    "Ionenstrahl- und Magnetronsputterverfahren für moderne Oberflächenanwendungen“

    Anwendungen bei der Fertigung von MEMS (Mechanisch-elektrische Mikrosysteme) erschließen zahlreiche neue Anwendungen für Plasma- und Ionenstrahlverfahren, insbesondere gilt das für die Fertigung von Baugruppen und Schaltkreisen für die Mobilkommunikation. Im Vortrag wird speziell auf Fertigungsverfahren für passive Hochfrequenzfilter eingegangen. Mit der modernen Mobilkommunikation hat sich die Hochfrequenzelektronik stürmisch entwickelt. Unterschiedlichste Informationen werden auf verschiedenen Frequenzbändern übertragen, so dass heutige Mobiltelefone bis zu 50 Frequenzfilter enthalten. Die Filter nutzen akustische Resonatoren, um eine notwendige Miniaturisierung vornehmen zu können. Je nach Frequenzbereich werden die Filter als Oberflächenwellenfilter SAW) oder Volumenresonatoren (BAW) ausgelegt. Der Vortrag stellt daher einleitend Anforderungen und Funktionsprinzipien dieser Filterbauelemente dar.
    In den Filtern werden piezoelektrische Materialien bzw. Schichtsysteme eingesetzt, die in geometrischen Dimensionen exakt auf die Zielfrequenzbänder eingestellt werden müssen. Über Magnetronsputtern werden einerseits piezoelektrischen Schichten mit hohen piezoelektischen Koeffizienten hergestellt, andererseits auch sogenannte Temperaturkompensationsschichten, die thermische Drift der Bauelemente zumindest einschränken soll. Trotz ausgefeilter Abscheideverfahren werden bei weitem nicht die Eigenschaftstoleranzen erreicht, um eine ideale Ausbeute an Filtern auf Waferlevel zu erzielen, daher müssen die Filter zwangsläufig auf die exakte Zielfrequenz getrimmt werden. Ein solcher Trimmprozess erfolgt durch verweilzeitgesteuerte Ionenstrahlen mittels deren Toleranzen bis in den sub-nm-Bereich korrigiert werden können. Der Vortrag präsentiert Verfahren, Ausrüstung und Ergebnisse zur Abscheidung der piezoelektrischen Schichten als auch zum finalen Frequenztrimmen der Filterbauelemente.
     
  • 11.12.2018
  • 18.12.2018
  • 08.01.2019

    Dr. Bridget Murphy , abstract - [Magnussen]
    (Institute of Experimental and Applied Physics, Kiel University
    Ruprecht Haensel Laboratory, Kiel University)

    "Archaeometry: The Role of Physics in the Quest to Understand Qumran“

    The famous Dead Sea scrolls, found in 1947 at Qumran, point to a group of people, the ‘Essenes’, described by famous philosophers including Pliny and Flavius Josephus. In 1998, interdisciplinary laboratory research started in Jerusalem between materials scientists, museum curators and archaeologists to obtain fresh information of what the manuscripts and the material culture may demonstrate, and how to preserve this cultural heritage for the centuries to come. While the primary question of ‘who wrote the scrolls and where’ remains unanswered this project opened a golden opportunity to employ archaeometry analytical techniques including structural analysis and spectroscopy to investigate the scroll parchment[1] and textiles[2] from Qumran[3]. In this lecture, I will explain how physics can provide non-destructive methods for investigating ancient artefacts. I will introduce the methods and explain how modern infra-red and florescence spectroscopic and neutron and X-ray methods can provide insight into the ancient practices and processes and also give us hints on how best to preserve these valuable antiquities.

    [1] B. Murphy, M. Cotte, M. Mueller, M. Balla, J. Gunneweg, in Holistic Qumran. (Brill, 2010), vol. 87, pp. 77-98.
    [2] M. Muller, B. Murphy, M. Burghammer, C. Riekel, E. Pantos, J. Gunneweg, Ageing of native cellulose fibres under archaeological conditions: textiles from the Dead Sea region studied using synchrotron X-ray microdiffraction. Applied Physics A: Materials Science & Processing 89, 877-881 (2007).
    [3] H. J.B., G. J., Khirbet Qumran et Ain Feshkha II, Novum Testamentum et Orbis Antiquus, Series Archaeologica 3. ( Academic Press Fribourg; Vandenhoeck & Ruprecht., Fribourg; Göttingen;, 2003).
     
  • 15.01.2019

    Prof. Dr. Karsten Danzmann (MPI für Gravitationsphysik und Universität Hannover), abstract - [Dau,Duschl]
    "Gravitational Wave Astronomy: Listening to the sounds of the dark universe!"

    For thousands of years we have been looking at the universe with our eyes. But most of the universe is dark and will never be observable with electromagnetic waves. Since September 14th, 2015, everything is different: Gravitational waves were discovered! We have obtained a new sense and finally we can listen to the dark side of the universe. The first sounds that we heard were from unexpectedly heavy Black Holes, which we are now routinely and frequently detecting. The observation of a neutron star merger opened the era of multi-messenger astronomy. Low-Frequency gravitational wave signals from supermassive black holes will soon be detected by the space detector LISA. And the laser technology developed for gravitational wave detection is now being used for earth observation with the GRACE Follow-on mission.
     

  • 22.01.2019
  • 29.01.2019

    Prof. D. C. Johnson (Materials Science Institute and Department of Chemistry, University of Oregon), abstract - [Rossnagel]
    "Materials by Design: Heterostructures with Targeted Nanoarchitecture and Tunable Properties"

    We have shown that by controlling the local composition of an amorphous intermediate on the nanoscale it is possible to kinetically control the self-assembly of new nanostructured compounds consisting of two or more compounds with different crystal structures that are precisely interleaved
    on the nanoscale. We have used this approach to synthesize hundreds of new metastable compounds with designed nanostructure, including structural isomers. Many of these materials have unprecedented physical properties, including the lowest thermal conductivities ever reported for a
    fully dense solid, systematic structural changes dependent on nanostructure, and charge density wave transitions. The designed precursors enable diffusion to be followed and quantified over distances of less than a nanometer, providing insights to the mechanism that gives control of the
    nanoarchitecture of the final product. We believe the ability to prepare entire families of new nanostructured compounds and equilibrating them to control carrier concentrations permits a new "thin film metallurgy" or “nanochemistry” in which nanostructure and composition can both be
    used to tailor physical properties, interfacial structures can be determined for precisely defined constituent thicknesses, and interfacial phenomena and modulation doping can be systematically exploited.

  • 05.02.2019
     

    PD Dr. Horst Fichtner (Ruhr-Universität Bochum, Institut für Theoretische Physik IV), abstract - [Heber]
    "Power Laws in Heliospheric Physics: Evidence for Nonlinear Diffusion, Anomalous Transport and Non-Extensive Entropy?"

    Numerous measurements of space plasmas and energetic particles by many spacecraft, including the two Voyagers that have by now both left the heliosphere, have revealed the almost ubiquitous presence of power-law behaviour of distribution functions both in velocity and in configuration space. Besides being indicative of acceleration and transport processes, such power laws have been considered as evidence for `non-standard' physics, particularly for so-called anomalous transport and for a non-extensive, i.e. non-additive entropy. The talk will demonstrate how heliospheric physics can contribute to answer related questions and, thus, how it is related to such fundamental aspects of physics.

  • 12.02.2019

    Dr. Jingnan Guo (Institute of Experimental and Applied Physics, Kiel University), abstract - [Wimmer-Schweingruber]
    "Understanding the Heliospheric Radiation Environment in Preparation for Human Explorations to Mars"

    Potential radiation damage to astronauts induced by Solar Energetic Particles (SEPs) and Galactic Cosmic Rays (GCRs) in space is one of the most important risks for future human space missions, especially interplanetary missions such as to Mars which requires a long mission duration of at least 2-3 years. To evaluate such radiation risks for deep space missions, in particular in preparation for future human explorations to Mars, the Radiation Assessment Detector (RAD) was designed to detect and analyze the most biologically hazardous energetic particle radiation during the cruise to Mars and on the Martian surface as part of the Mars Science Laboratory (MSL) mission.

    MSL was launched on November 26, 2011 and landed on Mars on August 6, 2012 after a 253-day, 560-million-kilometer cruise. During most of the cruise phase, RAD made detailed measurements of the cosmic ray (including SEPs and GCRs) radiation environment inside the spacecraft traveling through the space. The day after MSL's landing, RAD was switched back on and started making first-ever measurements of the cosmic ray induced energetic particle radiation environment on surface of Mars and has been collecting data for more than six years, approximately three years, since then. Both the deep-space radiation environment inside the spacecraft and the radiation field on Mars measured by RAD provide insight into the radiation hazards that be associated with a human mission to Mars and give indications of possible risk mitigation for future human explorations to the red planet.

    this talk, we review the RAD measurements since the launch of MSL and discuss the main results including (1) RAD measured cruise phase radiation environment and its (2) the Martian surface spectra and flux of energetic particles (both charged and neutral) detected by RAD and the validation of particle transport models based on these measurements, (3) the absorbed dose and dose equivalent rate from GCRs detected on Mars' surface and their time evolution influenced by both the atmospheric changes and heliospheric dynamics, and finally (4) the detected SEP events and their potential radiation risks.

  • 19.02.2019

    Prof. Dr. Friedrich Aumayr (TU Wien), abstract -  [Bonitz, Magnussen]
    "Probing 2D-materials by slow highly charged ions"

    Highly charged ions - along with femto- and attosecond light sources - provide a unique tool for probing the electronic response of solid materials to an extremely strong electric field, the Coulomb field of an approaching highly charged ion [1, 2]. In our experiments we study the ultrashort time response of different 2D-materials like graphene and MoS 2 to an incoming highly charged ion (typically Xe 40+ ). In a multi-coincidence setup [3] we measure the charge state and energy of highly charged ions transmitted through suspended 2D-membranes in coincidence with the number of emitted electrons. This allows us to derive the relevant time scales for charge transfer along the 2D-layer, the resulting current densities in the material and lower bounds for the breakdown currents. Depending on electron mobility some 2D materials fail to resupply the lost charges and/or fail to dissipate the absorbed energy on a timescale small compared to lattice vibrations. The resulting Coulomb explosion tears holes of the order of some nanometers into the 2D membrane [4], which are observed in high resolution (S)TEM investigations. The results of our studies are therefore of interest for engineering two-dimensional materials with electrons, ions, and lasers, with many prospective applications like their use as molecular sieves, for desalination or even DNA sequencing.

    [1] E. Gruber, et al., Nature Communications 7 (2016) 13948 (7 pages)
    [2] R. A. Wilhelm, et al. Physical Review Letters 119 (2017) 103401 (6 pages)
    [3] J. Schwestka, et al. Rev. Sci. Instrum. 89 (2018) 085101
    [4] R. A. Wilhelm, et al. 2D Materials 2 (2015) 035009 (6 pages)
    [5] R. A. Wilhelm, et al. Appl. Sci. 8 (2018) 1050 (16 pages)