Spatio-temporally resolved electron temperature in argon radio-frequency capacitive discharge at atmospheric pressure

Due to the lack of convincing experimental evidence for electron information, there are still unclearly understood discharge phenomena in atmospheric pressure radio-frequency (rf) capacitive discharge, e.g. the electron heating, discharge structures, and the alpha-gamma mode transition. Thus, to perceive basic and meaningful principles with an unambiguous interpretation, simple and reliable electron diagnostics are required. Since bremsstrahlung emitted through electron-neutral atom interaction depends on electron density (n_e) and temperature (T_e), their diagnostic is possible. In particular, T_e is easily estimated from the ratio of bremsstrahlung emissivities at two different wavelengths or more. In this paper, 2D T_e distribution in an argon atmospheric pressure capacitive discharge measured by using a digital camera and optical band pass filters is described. Time-averaged T_e in the bulk region obtained by a digital camera is consistent with that measured by an absolutely calibrated spectrometer. In addition, time-resolved emission spectra and the corresponding n_e and T_e during one rf cycle of the argon capacitive discharge are discussed. The result shows that T_e varied from 2.3 to 3.0 eV, while n_e did not change significantly.