Numerical study of the mode propagation along the plasmaline

Due to a growing demand for bottles made of polyethylene terephthalate (PET) fast and efficient sterilization processes as well as barrier coatings to decrease gas permeation are required. To allow for treatment of the inner surface of such PET bottles a specialized microwave plasma source - referred to as the plasmaline - has been developed. The plasmaline is a coaxial waveguide combined with a gas-inlet which is inserted into the empty bootle and initiates a reactive plasma. To optimize and control the the diverse surface processes, it is essential to fully understand the microwave power coupling to the plasma inside the bottle, and thus the electromagnetic wave propagation along the plasmaline. In this paper, we present a detailed dispersion analysis based on an analytical approach. We study how modes of guided waves are propagating under different conditions (if at all). The analytical results are supported by self-consistent numerical simulations of the plasmaline and the plasma.