Atmospheric-Pressure Air Plasma Jet and Its Striation Discharge Mode for Treatment of Thermally Sensitive Materials

A hollow inner electrode covered with a dielectric tube was inserted into an outer electrode and airflow was fed through the inner electrode. The electrodes were then connected to a transformer operated at an alternating voltage with sinusoidal waveform at a frequency of 20 kHz. The resulting discharge is ejected out of the outer electrode from a 0.7 mm hole in the form of a plasma jet into ambient air. The attributes of the discharged plasma jet were evaluated by monitoring the voltage and current behavior and by investigating the optical emissions. The discharge patterns in the atmospheric-pressure air plasma jet in the form of striations could be observed by the naked eye. Furthermore, we reported the striation mechanism by ion acoustic wave propagation by utilizing a simple calculation.