Diagnostics of an rf-excited micro atmospheric pressure plasma jet

The ``standard'' 13.56\,MHz rf-excited plasma jet operates at ambient conditions. It generates a homogeneous plasma in helium or argon with small admixtures (about 1 vol.-\%) of oxygen$^1$. Absolute concentrations of atomic oxygen have been measured in the effluent of the plasma jet by two-photon laser-induced fluorescence (TALIF). Even at several centimeter distance from the nozzle still there is 1\% of the initial atomic oxygen density of $10^{16}$\,cm$^{-3}$ present$^2$. Here we present a modified $\mu-$APPJ version particularly designed for investigation of the discharge interior. First emission spectroscopic investigations and tests of applicability are presented. The wettability of polymer Petri dishes could be adjusted in a wide range (wetting angle from 60$^\circ$ to below 10$^\circ$).\par \noindent$^1$ S. Wang, V. Schulz-von der Gathen, and H.F. Doebele, Appl. Phys. Lett. {\bf 83}, 3272 (2003)\\ $^2$ K. Niemi, S. Reuter, V. Schulz-von der Gathen, and H.F. Doebele, Plasma Sources Sci. Technol. {\bf 14}, 375 (2005)