Atmospheric pulsed DBD plasma jet for study on bacterial inactivation

A novel plasma jet with a plane-to-plane DBD structure working at atmospheric pressure has been developed. This jet is operated by a sub-microsecond pulsed voltage with a repetition rate of 1-10 kHz range. The working gas, helium, is fed into the plasma jet. The electrical property of the discharge has been studied by means of a classical DBD model. By fitting the fine structure of the emission bands of N₃ to a model, plasma gas is found to be cooled to near room temperature (~300 K) at 15 mm away from the jet nozzle exit, which is also verified by a thermocouple. Based on the analysis of the H_β Stark broadening, the electron density inside the plasma jet nozzle is evaluated to be in the order of 10¹⁴ cm^-3. Finally, the preliminary experiment confirmed the feasibility of disinfecting E.coli cells. It shows that adding oxygen could enhance the inactivating effect greatly and with 4% oxygen, the highest effect was obtained.