Thomson scattering diagnostics of atmospheric pressure plasmas - Pulsed filament discharges and plasma jets

Recently, non-thermal atmospheric-pressure plasmas have received much attention. Because the characteristics of the plasmas are governed by free electrons, measurements of the electron density ($n_{\mathrm{e}})$ and electron temperature ($T_{\mathrm{e}})$ are a prerequisite for understanding plasma behavior. To contribute to the understanding of non-thermal atmospheric-pressure plasmas, we have been developing a laser Thomson scattering (LTS) technique as a diagnostic method for measuring $n_{\mathrm{e}}$ and $T_{\mathrm{e}}$ of two types of plasmas; a pulsed-filament discharge and He flow plasma jet. The pulsed filament discharge has a short current width (a few tens of ns) and a small size. In order to apply LTS to such plasmas, reproducibility of time and space of the plasmas were improved using a high-speed semiconductor switch. Spatiotemporal evolutions of $n_{\mathrm{e}}$ and $T_{\mathrm{e}}$ of a main discharge have been obtained. Now we try to apply LTS at a time of primary streamer. Regarding to the He flow plasma jet, the discharge was generated with He gas flow with N$_{2}$/O$_{2}$(20{\%}) or N$_{2}$ shielding gas. It was confirmed that the $n_{\mathrm{e}}$ at the center of the plasma with N$_{2}$/O$_{2}$ shielding gas was around 50{\%} higher than that with the N$_{2}$ shielding gas.