The paper investigates a non-equilibrium atmospheric air plasma which is created with an AC discharge between a metal cathode and water anode with the gap distance of 1.3 cm. The current density in liquid electrode AC (60 Hz) glow discharge is tried to be obtained. OH emission intensity distribution is observed with high speed CCD camera. A band-pass filter is placed in front of the camera. The rotational and vibrational temperatures of N2 are found to calculate the composition of the plasma. Electron density in plasma is related with electrical conductivity and it is shown that electron density follows Gaussian radial distribution.
OH emission intensity distribution is captured by the camera. The cathode fall region, bright negative glow, positive column and anode dark space are observed as in glow discharges. A spectrometer is used to obtain the temporal emission intensity of OH. The output is transmitted to a wide-band oscilloscope and a relatively constant OH emission can be seen. They get the rotational and vibrational temperatures by comparing the simulations with the experimental results. The electron density can be found by knowing the current density which is also a function of electric charge and the drift velocity. The velocity depends on the reduced electric field (E/N) and it is constant along the half AC cycle. The electric field can be calculated with the applied voltage and the gap distance between electrodes. The current density is obtained by dividing the measured current by the area. As voltage and current increase in a cycle, electron density also increases, meaning conductivity increases and resistivity decreases. Therefore, the current density is directly related to the electron density. The width of the area is measured from the emission intensity spatial distribution which has a Gaussian profile.
With an AC discharge plasma, OH radical and N2 are investigated with a camera and a spectrograph. The electron density in plasma is measured using the conductivity.
Reference: Lu, XinPei, Frank Leipold, and Mounir Laroussi. “Optical and electrical diagnostics of a non-equilibrium air plasma.” Journal of Physics D: Applied Physics 36, no. 21 (2003): 2662.
Course: AME 60637