Instability Parameters of Optical Oscillation Frequency in Plasma Central Discharge and Periphery Region

We have observed relaxation oscillations in a capacitive discharge in Ar gas, connected to a peripheral ground chamber. The plasma oscillations observed from time-varying optical emission from the main discharge chamber show, for example, a high frequency (75.37kHz) relaxation oscillation, at 100mTorr and 8W absorbed power, and a low frequency (2.72Hz) relaxation oscillation, 100mTorr and 325W absorbed power. Time-varying optical emission intensity and plasma density are also detected with a Langmuir probe. The theoretical result agrees well with experiments.