Topic/Type: 1.5 Low-temperature, dusty and nano-plasmas, Invited
Jae Koo Lee
Pohang University of Science and Technology, Pohang 790-784, S KOREA
Very high-pressure plasmas at atmospheric pressure are one of the hottest research items of late. These modelings by using the conventional fluid or kinetic PIC (Particle-in-cell)[1-3] are particularly difficult as the plasma density becomes very high. These modelings esp. for biomedical applications are presented and compared against each other as well as against experiments. The physics of low-temperature nonequilibrium plasma discharges still remains not fully understood and the diagnostics of these atmospheric pressure plasmas are challenging and limited. In an attempt to overcome the experimental challenges, numerical techniques such as fluid, particle-in-cell and global models are often used to estimate plasma parameters. Fluid models which solve the particle, momentum, and energy equations are widely utilized in low temperature plasma because of low computational load. PIC models which track the super particles by solving Newton-Lorentz and Maxwell equations can capture the kinetics of electrons and ions. In this study, we focused on the comparison of results obtained from fluid and PIC models to provide guidelines on the effective models under the specific conditions. We varied driving frequency (of 10 kHz, 13.56 MHz, and 2.45 GHz) and the driving current density or the voltage in fluid and PIC models. The discrepancy between fluid and PIC models was increased with decreasing the driving frequency because of the difference of the electron energy probability function (EEPF) [2,3]. The global models of He/O2, Ar/O2, and N2/O2 solve particle and energy balance equations simultaneously and calculate densities of species and electron temperature to investigate the effects of the input power density and the admixture of oxygen.The maximum atomic oxygen density appeared at an admixture of 0.4% of O2 when the power was 330 Wcm-3. Ar/O2 produced higher densities of electron, atomic oxygen and ozone compared with He/O2 and the electron temperature of He/O2 was higher than that of Ar/O2 . As the impurity of water vapor increased, the production of OH radicals increased.
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