05.03.2015 - GAST: CLAIRE DOUAT
Post-doc Dr. Claire Douat (Eindhoven University of Technology) besucht vom 5.-31. März 2015 Postdoktorand Simon Hübner (Experimentalphysik II).
Her RAPID project ER2 is the "Design of dedicated equipment for time and spatially resolved measurements in atmospheric-pressure plasma". The scientific goal of this European project is the development of non-equilibrium (ie, the electron temperature is higher than the temperature of heavy species) reactive plasma sources that operate at atmospheric pressure. Operate at atmospheric pressure has the advantage to not require a vacuum system. In addition, more applications become possible such as plasma medicine, since the plasma can directly interact with a biological target.
For the development of this project it is necessary to diagnose the plasma in order to understand the physical and chemical phenomena taking place in the plasma and to control them for future applications.
RAPID ER 2
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.