Characterization of a nitrogen gliding arc plasmatron using optical emission spectroscopy and high-speed camera

A gliding arc plasmatron (GAP), which is very promising for purification and gas conversion, is characterized in nitrogen using optical emission spectroscopy and high-speed photography, because the cross sections of electron impact excitation of N₂ are well known. The gas temperature (of about 5500 K), the electron density (up to 1.5 × 10¹⁵ cm^-3) and the reduced electric field (of about 37 Td) are determined using an absolutely calibrated intensified charge-coupled device (ICCD) camera, equipped with an in-house made optical arrangement for simultaneous two-wavelength diagnostics, adapted to the transient behavior of a GA channel in turbulent gas flow. The intensities of nitrogen molecular emission bands, N₂(C-B,0-0) as well as (B-X,0-0), are measured simultaneously. The electron density and the reduced electric field are determined at a spatial resolution of 30 μm, using numerical simulation and measured emission intensities, applying the Abel inversion of the ICCD images. The temporal behavior of the GA plasma channel and the formation of plasma plumes are studied using a high-speed camera. Based on the determined plasma parameters, we suggest that the plasma plume formation is due to the magnetization of electrons in the plasma channel of the GAP by an axial magnetic field in the plasma vortex.