Spectral diagnosis of plasma jet at atmospheric pressure

Abstract

A new approach to surface modification of materials using dielectric barrier discharge (DBD) plasma jet at atmospheric pressure is presented in this paper. The emission spectral lines of argon plasma jet at atmospheric pressure were recorded by the grating spectrograph HR2000 and computer software. The argon plasma emission spectra, whose range is from 300nm to 1000nm, were measured at different applied voltage. Comparing to air plasma emission spectra under the same circumstance, it is shown that all of the spectral lines are attributed to neutral argon atoms. The spectral line 763.51mn and 772.42nm are chosen to estimate the electron excitation temperature. The purpose of the study is to research the relationship between the applied voltage and temperature to control the process of materials' surface modification promptly. The results show that electron excitation temperature is in the range of 0.1eV-0.5eV and it increases with increasing applied voltage. In the process of surface modification under the plasma jet, the infrared radiation thermometer was used to measure the material surface temperature under the plasma jet. The results show that the material surface temperature is in the range of 50~100 degrees centigrade and it also increases with increasing applied voltage. Because the material surface was under the plasma jet and its temperature was decided by the plasma, the material surface temperature increases with increasing the macro-temperature of plasma jet, the relationship of the surface temperature and applied voltage indicates the relationship of the macro-temperature of the plasma jet and the applied voltage approximately. The experimental results indicate that DBD plasma jet at atmospheric pressure is a new approach to improve the quality of materials' surface modification, and spectral diagnose is proved to be a kind of workable method by choosing suitable applied voltage.