Mathias Kaiser

Bifocal plasma source for treatment of gaseous pollutants

Abstract A new solution for plasma treatment of hazardous gases is presented. The main item of the concept is the concentration of microwave power, used to generate plasma and completed by a linearly extended bifocal device. Cold plasma up to 1 m in length and up to atmospheric pressure has been tested successfully with Argon at a gas flow of 0.4 m 3 /h and an average power of 2.8 kW. Initial experiments on pollutants in air gave a pressure limitation of the present set-up to approximately 100 mbar, due to the molecular nature of air components. It was found to be caused by the insufficient supply of pulsed microwave power limited through the experimental set-up available. Independent of that limitation it could be demonstrated that the actinism of the plasma on the pollutant is very effective. The significant destruction of halide, hazardous gases like trichlorethene and norfluorane could be demonstrated.

Numerical model of the plasmaline microwave plasma source

Summary form only given. Microwave generated reactive plasmas are due to their technical application and complexity high interest candidates for modeling by numerical simulation. Plasma models for some cases were developed by Stewart [1], Kousaka [2], Engemann [3] and others. This work focuses on the Plasmaline, a linearly extended microwave plasma source which is well suited to generate large-scale plasmas in the low-pressure range. Its use in industrial applications e.g. surface modification make it a fit target for simulation studies with the aim of facilitating the design of large-scale plasma devices and processes. For this intent a numerical model for Argon plasma was developed, solving the coupled system of Maxwell equations, continuity equations for electrons and metastable states and the electron heat equation. The solutions are self-consistently calculated with the COMSOL Multiphysics finite element simulation software. Our model can successfully predict the transient and spatial development of the sources plasma parameters (electron temperature, electron density) and field distribution for axial symmetric geometries. The simulations are in good qualitative agreement with experimental results. A quantitative verification will be implemented with a recently acquired plasma probe and will together with simulations of 3D models be pushing our model further towards the goal of an easy usable development tool for large-scale plasma sources.

A new linearly extended bifocal microwave plasma device

Abstract A new kind of linearly extended plasma source was developed. The prototype of such a device was built up as a barrel with elliptical cross-section. This bifocal shape has two focus lines. A linearly extended microwave antenna is placed along one focus line and the sector of plasma treatment is placed along the second focus line. The antenna is a linear emitter of radial divergent microwave radiation. In this work, a frequency of 2.45 GHz in pulsed and continuous wave (CW) mode was used. The power up to 6 kW CW and 10 kW pulsed is adjustable, pulse on/off times are variable in a wide field. The microwave is reflected by the metallic walls of the barrel and concentrated in the second focus line apart from the antenna. There a quartz tube is placed, that can be evaporated and filled with a working gas at a pressure between 10 2 and 10 5 Pa. The presented experiments have been done with Argon up to atmospheric pressure at a gas flow up to 6 slm.

Application of a MASWP: Duo_Plasmaline next generation

Summary form only given. Microwave based surface wave plasma reactors like those relying on the Duo-Plasmaline encounters large success in dielectric coating applications. But they show principal limitation to dielectric materials applications. We attempt here to present a Duo-Plasmaline NG based on the metal antenna SWP. This design would circumvent the dielectric coating limitation. The propagation length of the plasma will be reported as a function of gas pressure, microwave power and bias potential for different atmospheres like argon, nitrogen and oxygen. The plasma homogeneity will be reflected in the coating thickness evolution of a PECVD thin film along the antenna.

New microwave plasma sources for large scale applications up to atmospheric pressure

Summary form only given, as follows. Plasma technology is used in a wide field of applications for example for PECD-deposition, activation and etching. In particular microwave enhanced plasmas are very effective for activation of surfaces. Our objective targets are to construct plasma sources for large area application and plasma sources which can be used in a wide pressure regime as possible up to atmospheric pressure. In this presentation two sources for large area and wide pressure range plasma are discussed. They are based on a coaxial coupling of the magnetron and the antenna.