The Evolution of Characteristic Parameters and the Optical Information during the E-H Mode Transition in Inductively Coupled Plasma

The E-H mode transition of inductively coupled plasma (ICP) has been widely investigated due to its crucial role in the discharge process. The diagnostic of the parameters during the mode transition are important. In this study, the E-H mode transition characteristics under different gases (N2 and O2) and different pressures are measured and analyzed in detail, especially on the visible light characteristics evolution. It is found that the visible light characteristic changes of ICP before and after E-H mode transition are consistent with the changes in electron density and emission density, and opposite to the changes in coil voltage. In addition, as the gas pressure increases, the grayscale value of the discharge visible light images decreases, and the power required for the mode transition increases, corresponding to the changes in the electron density and emission intensity of spectra during the mode transition at different pressures. The results of this study provide a novel way for ICP E-H mode monitor using visible light image technology.