EP5
PROF. DR. TOSHIAKI MAKABE
Prof. Dr. Toshiaki Makabe (Vice-President Keio University, Yokohama / Japan) will be a guest of Prof. Czarnetzki (Chair of Plasma and Atomic Physics) from 23-24 February.
On 24.2. he will give two lectures on: 1) Today and Tomorrow in Keio University, Japan and 2) Formulation of momentum-transfer scattering at an inelastic collision on electron transport.
The talk (or the two talks) will have been held at 10:15 am in NABF05/694. Interested parties are welcome to attend!
EP2
CLAIRE DOUAT
Postdoc Dr. Claire Douat (Eindhoven University of Technology) besucht vom 5.-31. März 2015 Postdoktorand bei Simon Hübner (Experimentalphysik II).
Ihr RAPID-Projekt ER2 ist das "Design of dedicated equipment for time and spatially resolved measurements in atmospheric-pressure plasma". Das wissenschaftliche Ziel dieses europäischen Projekts ist die Entwicklung von reaktiven Plasmaquellen, die bei Atmosphärendruck betrieben werden und sich nicht im Gleichgewicht befinden (d.h. die Elektronentemperatur ist höher als die Temperatur der schweren Spezies). Der Betrieb bei Atmosphärendruck hat den Vorteil, dass kein Vakuumsystem erforderlich ist. Außerdem werden mehr Anwendungen möglich, wie z. B. die Plasmamedizin, da das Plasma direkt mit einem biologischen Ziel interagieren kann.
Für die Entwicklung dieses Projekts ist es notwendig, das Plasma zu diagnostizieren, um die im Plasma stattfindenden physikalischen und chemischen Phänomene zu verstehen und sie für zukünftige Anwendungen zu kontrollieren.
The project of the ER-2 position is to build a portable diagnostic, based on infrared absorption spectroscopy, to diagnose in terms of density of species, the different plasmas being used by the partners in the Network. A quantum cascade laser (QCL) is used as light source for this diagnostic.
Non-equilibrium plasma creates a multitude of species: positive and negative ions, electrons, and reactive atomic and molecular species, to just name a few. Some of the molecular species, such as CO, CO2, CH4 or NO, are able to absorb infrared light due to their molecular nature. It is similar to an optical filter: particular colors are not able to go through the plasma due to the presence of some molecules. As showed in Figure 1, the intensity of the light before absorption, I0, is higher than I. The Beer Lambert law formulates that by comparing these intensities, the density of the absorbing species can be known.
A quantum cascade laser is a laser able to emit a light in the mid-infrared. By changing the temperature of this laser, the main color of the laser can be tuned. However, this tuning has a limit range and to emit a laser with a wavelength outside this range, a different QCL must be used. In this project, the portable setup is composed of three different QCLs, which allows to measure the absolute density of several species, such as NO, CO and N2O.
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.
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).