Discharge characteristics of atmosphere pressure plasma jet in Ar

In order to study discharge mechanisms of atmosphere pressure plasma jet (APPJ) in Ar deeply and to optimize its discharge efficiency, the effects of outer electrode position on discharge characteristics and evolutions of APPJ in Ar were studied by means of electrical measurements of voltage and current waveforms and Lissajous figures, and by diagnosing optical properties on optical emission spectra and light-emission pictures. The main discharge parameters such as discharge power, transported charges, electronic excitation temperature, molecular vibrational temperature and molecular rotational temperature were calculated, the changing tendencies of them with applied voltage were studied, and the experimental results were explained by analyzing discharge mechanism. Results show that the effects of outer electrode position on discharge characteristics are mainly reflected in stage of plasma jet, and the electronic excitation temperature changes little with the positions of outer electrode. The generated APPJ in Ar plasm is a typical non-thermal one with gas temperature in the range of 317 K to 395 K, in which the main species are OH, N ₂, Ar and a little O. The outer electrode positions affect both the mode of the discharge and the breakdown voltage. When the distance from outer electrode to exit of tube is 40 mm and the applied voltage amplitude is 8 kV, the most intensified discharge with large discharge power and transported charges can be obtained, and the intensity of OH spectral line also reaches its peak. Therefore, when it is applied to surface modification of polymeric materials, the most efficient outcome can be achieved under the operation parameters.