Generation of microplasma jet at atmospheric pressure using a modified waveguide-based plasma torch

In this study, the microwave-induced microplasma jet was generated at atmospheric pressure using a modified waveguide-based plasma torch. To generate the small size plasma, the fine needle was set at the center of a circular hole made in a wider wall of rectangular waveguide with reduced height. Argon or helium gas was supplied to the free space through the needle. The jet type plasma was produced in a stream of small amount of gas at a few watts by 2.45 GHz microwave discharge at atmospheric pressure. In order to observe fine structure of the plasma produced using fine needles, images of jets were observed by using a stereo-microscope. The dynamics of the plasma jet was also investigated by means of a gated intensified charged-coupled device (ICCD) camera. Different plasma structures were observed for argon and helium. It is considered that the thermal conductivity of the discharging gas mainly affected the structure of the plasma jet.