Atmospheric pressure micro-plasma in a single pin-electrode configuration

Summary form only given. A micro-plasma of non-transferred jet type was produced in the ambient air using a single pin electrode of radius 360 im and a low frequency power supply. Then, its characteristics, such as size and light emission, were studied. A typical operation condition was the input voltage of about 1000 V at the applied frequency of 50 kHz and the helium flow rate of 4 lpm. The plasma was lengthened towards the helium flowing direction, making a long and thin cylindrical shape. It was as long as about 30 cm at 1500 V. The plasma length and radius could be varied for a quite large range by controlling the experimental parameters such as the input voltage and the gas flow rate. The emission spectra showed helium lines (587 nm, 706 nm etc.) with a few nitrogen and oxygen lines (391 nm and 777 nm) due to the air molecules. The measurement of optical emission intensity was performed as the measurement position, the input voltage, and the helium flow rate were varied. At the electrode tip, the emission was discrete and different for each half period of the input voltage. For instance, during the positive half period of the input voltage, the emission was broader in time. However, at further away from the electrode tip, there was no emission during the negative half period. The emission intensity, integrated over one period of the input voltage showed that it was increased with the input voltage and was maximum at the helium flow rate of 4 lpm