Discharge characteristics of atmospheric-pressure microplasma jets

Atmospheric-pressure plasma jet (APPJ) has been considered to use in various biomedical applications due to their convenience to generate highly reactive oxygen and nitrogen species in ambient atmosphere. Capillary dielectric barrier discharge (DBD) for the APPJ is widely used. In this study, we investigated how electrode length affects the discharge characteristics such as breakdown voltage and sustain voltage. Also, we investigated the gas discharge with typical glass tube as well as alumina tube with tapered nozzle exit. High voltage up to 11 kV with a low frequency at 9 kHz was applied for the helium gas flow rates varied up to 2.5 L/min and electrode length was varied between 5 and 25 mm. In the result, both the breakdown and sustain voltages were relatively higher for the alumina tube than for the glass tube. Specifically, the breakdown voltage with electrode lengths of 15 mm or less was approximately 7.5 kV<sub _mstmutation="1">p-p for the alumina tube and 7.0 kV<sub _mstmutation="1">p-p for the glass tube, respectively. In both materials, a relatively higher breakdown voltage was necessary. It was noticed that the electrode length to be 20 mm or more in the case of alumina tube, while 40 mm or more for the glass tube. Furthermore, a significant increase of the sustain voltage was also measured with the alumina tube.