Optical and electrical diagnostics of a non-equilibrium air plasma

Abstract

An AC-driven, non-equilibrium, atmospheric pressure air plasma is generated within the gap separating a disc-shaped metal electrode and a water electrode. The typical OH emission intensity distribution is recorded by high-speed CCD camera. The temporal emission behaviour of OH(A–X) shows that the OH emission intensity stays relatively constant during most of the current cycle but decreases abruptly when the current is close to zero. The N2 rotational and vibrational temperatures are obtained by comparison of the simulated spectra of C 3Π u–B 3Πg (Δv = −2) band transition of nitrogen with the experimental results. They are about 1800 K and 2600 K, respectively. The electron density in the plasma is measured utilizing the electrical conductivity. It is found to be 7 × 1012 cm−3 in the centre of the discharge during the peak current of Ipeak = 40 mA. The electron density follows a Gaussian radial distribution with a typical width of 0.35 mm.