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TP4
DR. ILAN ROTH
From April 28-30, 2015, Dr. Ilan Roth from Space Sciences UC Berkeley, University of California, USA will be a guest of Prof. Dr. Reinhard Schlickeiser (Theoretical Physics IV). As part of the seminar "Space and Astrophysics" he will give a talk on "Knotty Invariants: Structure & Evolution of Magnetized Fluids" on 4/29 at 10:15 am (NB 7/67) and on "Solar/Planetary/Galactic Relativistic Electrons: Common Denominator?" on 4/30 at 10:15 am (NB 7/67). Interested parties are welcome!
ABSTRACT "KNOTTY INVARIANTS: STRUCTURE & EVOLUTION OF MAGNETIZED FLUIDS"
Magnetic fields in the laboratory and in space are generally depicted as closed loops or curves anchored at physical foot-points, both deformed through a set of stretching and bending procedures. This classification allows one to describe most of the magnetic configurations in fusion research, in magnetic confinement and in astrophysical environments as 2D curves modified by slide, poke or twist.
However, dynamically evolving 3D magnetic structures may form loops which cannot be transformed to an equivalent closed (anchored) two-dimensional curve. Hence, the resulting curves' characterization may be generalized through their unique topology. The analogy between MHD and knot theory offers a new classification of magnetic flux tubes. Ideal MHD fluid describes non self-intersecting loops with smooth stretching and bending in the viscous surrounding fluid, identically to mathematical knots. The crossings of a 3D structure projection are assigned mathematical operations resulting in new invariants which are preserved under stretching and bending, forming robust entities. We conjecture that the field which emerges from the solar photosphere appears in the form of a prime knots, knots which cannot be composed from two nontrivial knots. Observations of intermittent ion flux drops in impulsive solar flares can be attributed to the formation of the simplest knotty structures – torus knots. Similarly, accumulation of small-scale localized spatial structures seen in simulations and inferred experimentally in the cascading solar wind plasma can be related to the stability of the 3D knots. Implications for dynamo processes and decay and for stability of complex magnetic configurations due to preservation of topological invariants are suggested.
ABSTRACT "SOLAR/PLANETARY/GALACTIC RELATIVISTIC ELECTRONS: COMMON DENOMINATOR?"
Observations of electron distribution functions with sub or super relativistic tail or power law(s) at high energies and with elongated tails are common in space plasmas. These distributions are measured in situ or deduced remotely in various magnetized environments. The in situ measurements relate to enhanced fluxes of relativistic electrons principally (i) in the terrestrial outer radiation belts and (ii) at the interplanetary medium at heliospheric distances of 1 AU with related solar observations, or (iii) remotely at galactic distances through various radiation emissions. Due to the similarity between the observations at the relativistic radiation belts and solar electrons it is suggested that a specific bootstrap mechanism to relativistic electrons operates at these environments. Several possible solutions to previously ignored aspects of the mechanism will be offered. New mathematical description for the formation of an energetic distribution function tail will be described.
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EP5
PROF. DR. YI-KANG PU
Prof. Dr. Yi-Kang Pu from the Department of Engineering Physics at Tsinghua University (China) will be a guest of Prof. Dr. Uwe Czarnetzki (EP5) from April 4-9, 2015.
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MEET AND GREET - WOMEN IN PLASMA
The SFB-TR 87 invited female scientists to the first „Meet and Greet – Women in Plasma“, an event focused on the exchange and networking of women involved in plasma science. The get together took place in the evening (6:30pm) of March 20th, 2015 at Hotel Meliá in Düsseldorf.
link to Women in Plasma
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DR. SIMON HÜBNER AN DER TU EINDHOVEN
Vom 23. März bis zum 1. Mai 2015 ist Postdoc Dr. Simon Hübner (Experimentalphysik II) zu einem Forschungsaufenthalt an der TU Eindhoven (Niederlande).
Foto von links: Simon Hübner, Claire Douat von der TU Eindhoven, Joao Santos Sousa vom LPGP, University Paris Sud und Ana Sobota von der TU Eindhoven.
link to ER-3 Materials design using reactive atmospheric pressure plasmas
MATERIALS DESIGN USING REACTIVE ATMOSPHERIC PRESSURE PLASMAS
The present day society needs coatings. That is for various high and low-tech products, such as wear-resistant coatings on plastic parts or barrier coatings to keep delicate food in good containment. Then there is the large field of coatings for optics, such as the popular anti-reflective coating on glasses. But one should keep in mind that also more or less all modern optical technologies like lasers will hardly work without such coatings.
A different approach is to treat surfaces without necessarily any deposition in order to a lter its properties. In this way for example plastic surfaces can be varied from extremely water-loving to water-repellant. Or specific medical active compounds, like antibiotics can be bound to surfaces.
In order to promote the necessary chemical reactions, the industry usually relies on simply heating and reactive chemicals, sometimes toxic, sometimes very inefficient. On the contrary, plasmas have the unique ability to promote non-equilibrium chemistry. That means a chemical reaction is induced without the reaction partners have to be hot or in a chemical reactive state. It is like conversion of electricity, to drive the plasma, to bonding energy of atoms and molecules.
An even more convenient way to achieve such things is using atmospheric pressure plasmas. The investment to build the plasma source is significantly reduced and delicate materials can be treated as well. However, it is not that simple. Atmospheric plasmas are by nature small in size, as pressure times diameter is somewhat constant. Another challenge lies in the high density of atmospheric pressure gas. An energetic particle created in the plasma is lost very rapidly because of the huge amount of collisions and the non-equilibrium nature does not work well. Clever ways have to be thought of to bring the energy carried by ions and highly excited species from the plasma to the target.
A part of this project is the study of these ‘plasma-activated’ atoms and molecules. That can be achieved by mass spectrometry. Specific ions and neutrals can be counted and in case of neutrals even absolute densities are measured. As the detection has to be in low pressure, a multi-stage system is used. With these techniques the nature of the dominant ion emanating from the plasma can be determined or the dissociation degree of e.g. nitrogen or oxygen can be found.
The second major part in this project is the film characterization. For instance organosilicon molecules, can be added to the plasma and form a SiO-like layer on a substrate. Now, the different degree of oxygen added to the process changes dramatically the amount of carbon present in the film. The latter can be studied very well by infrared absorption of the molecular bonds.
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EP2
REMI DUSSART UND VALENTIN FELIX
From March 16-18, 2015, Prof. Dr. Remi Dussart and PhD student Valentin Felix from GREMI are guests of Dr. Volker Schulz-von der Gathen and PhD student Judith Golda. Valentin will stay until March 20. Pascal Vogel, who was at GREMI for six months via Erasmus and developed the arrays with Valentin as part of a project with Remi Dussart, will also be there and is currently being tested.
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TET
DR. SVEN ZIMMERMANN
On March 24, 2015, Dr. Sven Zimmermann from the TU Chemnitz and the Fraunhofer Institute for Electronic Nano Systems, respectively, will give a lecture in ID 04/401 as part of the Faculty Colloquium (Eletrotechnology and Information Technology). The title is "28 nm Technologies and Beyond: Challenges of Plasma Processing". Interested parties are cordially invited.
Dr. Sven Zimmermann is a guest of PD Dr. Thomas Mussenbrock (TET).
Kolloquiumsvortrag Sven Zimmermann
ABSTRACT: Plasma patterning processes play a key role in modern ULSI device fabrication. With further
scaling of device dimensions plasma process characteristics become more and more the
limiting factor in pattern minimization not least due parasitic effects caused by different plasma properties. Such effects are notching, footing and source/drain destruction during high-k/metal-gate patterning as well as the most critical sidewall damage while etching trenches an
d vias in back-end of line technologies for ultra low-k dielectrics. Finally the charge
damage of thin gate oxides during plasma processing results in decreased reliability and function
ality of completed devices. The lecture overviews typical challenges during plasma patterning processes in 28 nm and 22 nm technology nodes by means of today’s back-end of line integration schemes. Different plasma diagnostic methods give an insight into physical and chemical conditions
of different etch chambers and their influence on process results and damaging behavior.
Finally a plasma assisted chemical repair process for etch damaged ultra low-k sidewalls will
be introduced. This process bases on the fragmentation of different organosilicon molecules using in a downstream plasma chamber, whereby significantly enhanced repair efficiency can be achieved.
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EP5
THIERRY BELMONTE
Prof. Thierry Belmonte and his people have visited from March 9th-12th, 2015 the group of Prof. Czarnetzki. Prof. Belmonte (Institut Jean Lamour, Nancy, France) is investigating pulsed discharges in liquids (liquid nitrogen, water, alcohols) for generation of variety of nanoparticles. Because the jitter of the discharge ignition time and the pulse-to-pulse differences among the formed microdischarges are large, it is very difficult to obtain reliable time-resolved information about discharge performance. An ideal diagnostics for such discharges is a use of streak camera. This camera has been provided to plasma researchers in Bochum by Germen Science Foundation (DFG) in frame of Research Unit "Physics of Microplasmas" (FOR 1123) and has been now successfully applied to the discharge of Prof. Belmonte with the assistance of AvH stipend Dr. Emile Carbone and PhD student Patrick Böhm. These activities are suported by a Leverhulme Trust lnternational Network Collaboration "Materials processing by atmospheric pressure plasmas for energy applications", initiated by Dr. Davide Mariotti (University of Ulster, Jordanstown, Northern Ireland) and includes also Jun.-Prof. Jan Benedikt (Ruhr-University Bochum) and Dr. Vladimir Švrček (National Inst. of Advanced Industrial Sci. and Techn. (AIST), Tsukuba, Japan).
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TET
DR. ZOLTAN DONKO UND DR. PETER HARTMANN
From March 2 to 6, 2015, Dr. Zoltan Donko and Dr. Peter Hartmann from the Wigner Research Center for Physics of the Hungarian Academy of Sciences were guests at the Chair of Theoretical Electrical Engineering in Bochum. This provided many opportunities for intensive collaboration and exchange on the mechanism of electron heating in capacitively coupled low-temperature plasmas. The stay was funded by the German Research Foundation in the framework of the Collaborative Research Center Transregio 87.
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EP2
PROF. GOTTLIEB OEHRLEIN
Prof. Gottlieb S. Oehrlein will spend part of his sabbatical with Prof. Achim von Keudell (Experimental Physics II) in April 2015. He is coming from the Department of Materials Science and Engineering, Institute for Research in Electronics and Applied Physics at the University of Maryland, USA and will give a talk on "Low temperature plasma research at the university of Maryland" on 4/20/2015 at 9:15 am (seminar room EP2, NB 5). In this context, he will also offer a small crash course on "A brief overview of materials processing using low temperature plasma" on 4/27/2015, 13:00-17:00.
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TET
PROFESSOR ISMAIL RAFATOV
Assoc. Professor Ismail Rafatov from the Physics department of METU visited TET on 11 March 2015. He presented detailed seminars on the three different topics of his expertise: (1) Overview of the main modelling approaches (kinetic/particle, hybrid, and fluid) for gas discharge plasmas, (2) Modelling in COMSOL Multiphysics: "Equation based" model vs. COMSOL Plasma Module and (3) Chaos and pattern formation in low-temperature plasmas. In the seminars the basic modelling approaches for the gas discharge plasmas were outlined. Finally, a detailed analysis of spatial and temporal pattern formation in a dc driven "barrier" discharge system was presented. In the case of purely temporal oscillations, a transition of the system to chaos through period doubling bifurcations cascade could be identified. Beyond the initial transient regime, numerical solutions reproduced the Hopf or Turing-Hopf instability of the homogeneous stationary state. The agreement between 1d, 2d, and 3d numerical simulations and a linear stability analysis (within its range of validity) were also demonstrated. The visit was sponsored by the German Research Foundation in the frame of the transregional collaborative research centre TRR-87.
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DPG Spring Meeting Plasma Physics & Short Time Physics 2015
Location: Audimax Foyer & Lecture Hall Center East (HZO), RUB
Date: 2-5.3.2015
http://bochum15.dpg-tagungen.de/index.html