Invited Paper PS1-ThM3
Generations, Characterizations and Applications of Microplasmas Operated in Atmospheric Gases and Artificial Media

Thursday, October 23, 2008, 8:40 am, Room 304

Microplasmas of sub-millimeter to micrometer scales can be operated in high pressure gases or high density media with a choice of single or integrated usage. The electron density n_e of a typical microplasma lies in the range of 10¹² to 10¹⁵ cm^-3 even though the ionization degree is rather small. As for the electron temperature T_e, it shows non-equilibrium natures inherently due to the short residence time in small space or short duration of pulsed discharge in the generation. Taking the advantage of these non-equilibrium properties, microplasmas have been applied to various purposes such as material syntheses, surface treatments, environmental and biomedical issues, etc. In this talk, I would like to introduce some examples of new schemes of microplasma sources with their characterizations by various diagnostic methods; we have been applying optical emission spectroscopy (OES), laser absorption spectroscopy (LAS), and laser-induced fluorescence spectroscopy (LIF) for the measurements of excited and ionized species as well as THz time-domain spectroscopy (TDS) and infrared CO₂ laser heterodyne interferemetry for plasma parameters. In addition to the microplasma generation in usual gas phase, we have been trying to use atmospheric gases with liquid vapors (mists) and aqueous solutions with micro bubbles as artificial media of microplasmas under controlled (characterized) conditions. As one of the examples, by using a fabric electrode assembly weaved with insulated wires, we have succeeded in the generation of microplasmas in H₂ or O₂ bubbles produced underwater by electrolysis. Those results will be explained together with some examples of their potential applications.