Aiaa 2000-0202 Boundary Layer Diagnostics of an Atmospheric Pressure Plasma Jet

Measurements of species concentrations and temperature are performed in the boundary layer of an atmospheric DC plasma assisted chemical vapor deposition (CVD) system. Broadband ultraviolet absorption spectroscopy is employed to measure absolute number density of C2 and CH radicals. Stark broadening of Hβ emission is utilized to determine the electron number density inside the boundary layer. The temperature profile obtained by measuring the peak separation of C2 P-R branches of DΣ → XΣ electronic transition is compared with a onedimensional numerical model. Optical emission spectroscopy of CN B Σ→X Σ is used to confirm the freestream temperature measurement. The measured super-equilibrium number densities of C2, CH and e in the plasma jet indicate that chemical nonequilibrium exists in the thermal plasma due to limited flow reaction time. The measured temperature profile and C2 concentration agree well with the numerical simulations in the boundary layer near the substrate.