Characteristics of atmospheric pressure micro-plasma jets in two different modes of excitation depending upon wave amplitude and frequency

The plasma characteristics of atmospheric pressure micro-plasma jets in two different modes of excitation: low frequency (∼10 kHz), high voltage (∼15 kV) (LFHV) and high frequency (∼80 kHz), low voltage (4 kV) (HFLV), are investigated. The effect of AC electrical excitation on the plasma, depending upon wave amplitude and frequency, are looked at experimentally in the two systems. Plasma parameters such as the electron density (ne), electron excitation temperature (Texc), including optical line intensities from different species in the plasma are investigated as a function of applied external voltage, gas flow rate and operating frequency. Electrical modelling of the two different plasma systems are carried out and the results from the models are found to agree reasonably well with those of the experiments. It is found that the electron density and the temperature of the HFLV system are higher than the LFHV system at a particular gas flow rate, although the external applied voltage is higher for the LFHV system. A lower value of Texc for the LFHV system may make it suitable for medical or biological applications. Since a large electric field is created near the tip of the pin electrode in the HFLV system, therefore even though the applied voltage is lower than the LFHV system, the plasma can be easily generated. The HFLV system support a higher Texc, and such a system could be useful for material surface modification applications.