Abstract
Atmospheric pressure plasma jets (APPJs) have attracted a great deal of attention recently since they do not need expensive vacuum system, enabling a wide variety of application such as surface modification or bio-medical treatments, etc. As can be seen, APPJs produce non-thermal plasmas where extremely high electron temperature (1~2 eV) and active plasma species are generated when radio-frequency powers are applied. In this thesis, we summarized the mechanisms of applications and found that the gas temperature and the reactive oxygen species (ROS) generated in plasma plume are strongly related with the effect of applications. Then, we investigated various types of APPJs and their parameters including effects of frequencies, gas compositions and configurations. Also, we studied simulation and experiment results of world-wide groups in order to take their research methods as references. After the investigations, we realized that to low the power consumption and temperature for APPJs, a Multi-electrode dielectric barrier helium/oxygen discharge coupled with radio-frequency power might be able to achieve low power consumption (low gas temperature) and wide range operation. In this thesis, we investigate the characteristics of radio frequency multi-electrode Helium/Oxygen atmospheric pressure plasma jets (RF ME He/O2 APPJs) by simulation and experiment. For simulation, a two-dimensional (2-D) fluid model for numerical analysis using ESI CFD-ACE+ was developed. For experiment, on the other hand, an experimental configuration was set up with impedance and optical emission spectroscopic (OES) measurements. Simulation results represents the 2-D distributions of electron density and reactive species vary with times and reach to the steady states. The results also show the sustain voltage in typical case for ME APPJ. Also, they point out that the atomic oxygen (O), metastable oxygen (O2*) and ozone (O3) are main reactive oxygen species (ROS) generated by plasma and the main reactions for ROS formations. After doing the parameter optimization, we found out ME APPJ ignited with 1.5 W, 3 m/s and 0.3% O2 mixed might be achieve low power consumption and high ROS generation according to the simulation results. For experimental results, we show the photograph of ignited plasma plume in order to demonstrate the distribution of plasma. Also, with impedance and OES measurement, I-V curve and optical spectra of helium/oxygen discharge are presented. From the spectra, the reactive species in discharge are investigated. Moreover, the emission ratios of noble gas transitions that quite apart in wavelength at different voltage are presented. We found out an increasing trend as voltage rising up. Therefore, for future works, the short term is to carry out the effects of gas composition in open air since the spectra shows that reactive nitrogen species (RNS) are also important for discharge. Once the analyses are done, the experimental structure will be adopt for applications as well. For the long term, we will do surface treatment for glass substrate and heat-sensitive materials. Water contact angle measurement will also be considered to estimate the densities and distributions of reactive oxygen species generated by plasma plume.