Study On Optical Diagnostics And Mode Of RF Argon Capacitive Discharge In Atmosphere

In this paper, the characteristics of RF argon capacitive discharge at atmospheric pressure with the structure of fiat-plate electrodes are investigated by electrical measurements and optical diagnostics.The existence of two discharge modes named a and y mode were found under specific conditions, the holding voltage of two discharge modes are different in different gas pressure. The holding voltage of a mode is higher than the holding voltage of y mode in atmospheric pressure. So a mode to y mode transition at higher voltage will be investigated. The mode transition and coexistence were found in atmospheric pressure argon RF capacitive discharge. In this paper, according to the change of Current-voltage characteristics, the mode transition was affirmed, and answered to the photograph of discharge.The emission spectra of N2 (C3Πu→B3Πg) and OH (A2Σ→X2Π) were observed due to the atmosphere surrounding. By use of a program compiled by the authors for the nitrogen's second positive band simulation, comparison between the experimental and simulated spectra of band (0,1), (1,2) was used to determine the rotational and vibrational temperature of N2. The trend of vibrational and rotational temperature with discharge power was studied to observe the temperature jump corresponding to the discharge mode transition. Utilizing a well-known software named Lifbase, the simulated spectra of OH (A-X) (0,0) was calculated to obtain the rotational temperature of OH by comparing with the experimental OH (A-X) (0, 0) band. The resultant rotational temperature of OH is well consistent with the result of nitrogen's second positive band, which shows that the neutral species are at thermal equilibrium in the space of discharge. Excited temperature was about 2800K attained by Boltzmann equation, and excited temperature not evidently changes versus the change of power. Electron temperature was estimated on the basis of excited temperature. The theory of infrared thermal imager was introduced. Gas temperature was measured using infrared thermal image, and answered to rotational temperature.